Looking for some space-based thrills and chills to enjoy this Halloween? Have no fear – or have a lot of fear, actually – Star Trek has you covered! We’ve listed 28 of the scariest episodes from across the franchise in order of just how much they freaked us out, so whether your preference is for deep space exploration, war-torn space stations, or the far reaches of the known universe, there’s something here for you.
This list excludes all of the feature films, which tend to be scarier on the whole as they’re aiming to make an impact on a cinema audience (Star Trek II: The Wrath Of Khan and Star Trek: First Contact have some especially terrifying sequences). It also excludes The Animated Series and Lower Decks. The Animated Series is seriously under-rated, but it’s bright, colourful style and slightly lighter tone don’t really bring the scares. Lower Decks features lots of blood, guts, gore, zombies and a giant spider to rival Shelob – and that’s just in the first episode! – but it’s basically satire, so none of it really comes across as scary.
This list is also firmly focused on spooky Halloween chills. There are many, many episodes of Star Trek from across the franchise that deal with torture or moral murkiness. We’re not looking for episodes that will make you question whether it’s possible to be a good person in a harsh universe, but for classic horror movie scares – creepy set-ups, scary scenarios, and spooky chills.
28. The Original Series: season 2, episode 7 ‘Catspaw’
This episode isn’t really all that different from the many The Original Series episodes where some implausibly powerful alien being plays dangerous games with the crew that include a hefty dose of fantasy, but the Halloween-style setting gives it a spooky vibe. Captain Kirk tries to use his sexual allure to solve the problem, of course, and completely disrupts an alien relationship through sheer force of his masculinity. But all is well in the end, though the scene where the villain uses sympathetic magic to over-heat the Enterprise as she dangles a model of it over a candle flame is pretty freaky.
One to avoid if you’re scared of: Cheesy Halloween set-ups.
27. Voyager: season 5, episode 18 ‘Course Oblivion’
The idea that you might not be who you think you are has a clear existential horror to it, and this isn’t the only episode on this list based on that concept. It’s really more sad than scary as the truth of the situation is discovered about halfway through, and once the entire crew realise they’re not human after all, but recent copies of the original Voyager crew, they’re too concerned with the fact that they’re dying in vast numbers to dwell much on the personal horror of their position. Even knowing they aren’t the original crew, watching these beloved characters die one by one is gut-wrenching, and the final moments are truly the stuff of nightmares – they’re so close to help, but just can’t cry out…
One to avoid if you’re scared of: Disintegration, ship-wide destruction.
26. Enterprise: season 2, episode 4 ‘Dead Stop’
Creepiness doesn’t have to come from old houses, dark streets, and rooms full of shadows. It can also come from bright, white light and empty spaces. Threats don’t have to be immediately obvious – they can come cloaked in what looks like kindness and generosity. With creepy direction from Voyager’s Roxann Dawson, who also voices the mysterious computer, and the always unnerving theme of a computer killing organic lifeforms, this creates an unsettling vibe without the schlocky Halloween staples. Throw in a classic fake order from a convincing-sounding voice, the apparent death of a regular character (not an uncommon occurrence on Star Trek, it has to be said), and Archer’s desperate plea, familiar to all of us who’ve ever called a helpline, of “I need to talk to a person!”, and you’ve got a pleasantly unsettling hour of television.
One to avoid if you’re scared of: Automated telephone helplines.
25. Deep Space Nine: season 2, episode 14 ‘Whispers’
This isn’t the only episode on this list about the horror of discovering you aren’t who you thought you were, or about a family member who isn’t their usual self. But it does offer a different, and equally disturbing, take on the idea. For most of this episode, we follow Chief O’Brien as he returns to Deep Space Nine, only to find the behaviour of everyone around him is just a little… off. The ending is tragically moving, but the bulk of the episode is increasingly disconcerting, with O’Brien unable to trust anyone or to work out what could possibly have happened while he was away. It plays into fears deeper than the fear of things that go bump in the night – the fear that your friends and family might drift away from you, or turn on you, or pull apart from you. And that’s one of the scariest things of all.
One to avoid if you’re scared of: Being abandoned, your boss and colleagues turning on you.
24. Voyager: season 6, episode 25 ‘The Haunting Of Deck Twelve’
Voyager’s Borg children get a campfire story from Neelix addressing the apparently ‘haunted’ Deck 12. It’s a space alien, of course, but it has its moments providing some good scares and another opportunity for the Voyager crew to nearly abandon ship (something they make more of a habit of than they should considering they’re lost in the Delta Quadrant). The campfire ghost story set-up adds a nice sense of Halloween fun to the tale, there’s some nice character work (Neelix’s frequent fear of darkness and nothingness comes up, and his love/hate relationship with Tuvok) and there are some scary moments – after all, how do you outrun a gas cloud?
One to avoid if you’re scared of: Gas, nebulas.
23. The Next Generation: season 7, episode 19 ‘Genesis’
This one is too terrible an episode to get any higher on the list – we really can’t recommend it as an actually good episode of Star Trek. But it’s here because you can’t deny that as the Enterprise crew slowly de-evolve and regress to earlier phases of evolution from their respective species, the effects are genuinely unnerving, as well as occasionally laughable. Voyager’s ‘Threshold’ (frequently referred to as the worst episode of Star Trek of all time) similarly includes some effective body horror before it descends into ludicrousness and people start turning into lizards and abandoning their lizard babies, but is too silly to include – this one, however, hangs on just long enough to produce some real scares. It helps that the crew are de-evolving, rather than evolving into an apparently higher form.
One to avoid if you’re scared of: Spiders, lizards, lemurs, and terrifying human-animal hybrids.
22. The Next Generation: season 4, episode 17 ‘Night Terrors’
One of several ‘waking nightmare’ episodes, this one is let down a bit by the somewhat unconvincing scenes of Troi flying through a weird green skyscape, but there are plenty of properly creepy moments to enjoy. Dr Crusher’s hallucination of a roomful of corpses sitting up is a standout, but Picard thinking the turbolift is shrinking in on him is alarming too, and the scraps of audio revealing what happened to the late crew of the USS Brattain, who murdered each other in the grip of paranoid hallucinations, are chilling. The science behind the idea, that we need REM sleep to be able to function, is solid, which makes the whole thing even more frightening.
One to avoid if you’re scared of: Corpses, insomnia.
21. Voyager: season 2, episode 8 ‘Persistence of Vision’
Over the course of seven years, Voyager did so many episodes in which almost the whole crew were knocked out, suffered from hallucinations, put to sleep in a collective dream or otherwise mentally trapped by aliens, that they made a reference to it in season seven’s ‘Shattered’. This one is a good choice for Halloween, though, thanks to some nicely spooky imagery. It featured Janeway’s Victorian Gothic holo-novel and so her hallucinations include a ghostly little girl in Victorian clothes having a tantrum about cucumber sandwiches, which is particularly unsettling. It also features an unusually ‘evil’ and mysterious villain who has no motive other than being a nasty character and vanishes into thin air, and allows Kes to really shine at the climax, showing off her own considerable powers.
One to avoid if you’re scared of: Creepy children, massive boils leaking pus.
20. The Next Generation: season 1, episode 25 ‘Conspiracy’
This episode is remembered for one thing and one thing only – the exploding head. And the alien chest-burster incident that comes right after it. Although the ending seems to hint at a wider threat, it was never officially followed up on within the series, possibly partly because this episode was so much gorier than anything seen on Star Trek up to that date. It also experienced some mutations of its own in development. What was originally intended to be a conspiracy within Starfleet was nixed by then-still-alive Gene Roddenberry as not conforming to his utopian vision. Perhaps this is why, to make up for the less psychologically disturbing conspiracy-by-alien-outsider, the production team went all out on the gore at the episode’s climax. It’s certainly memorable!
One to avoid if you’re scared of: Gore, alien chest-bursters.
19. Voyager: season 3, episode 18 ‘Darkling’
Robert Picardo hams it up gloriously in this homage to Jekyll and Hyde. The idea behind the episode, that when the Doctor patches the personalities of famous people into his program he gets their dark sides as well as their good qualities, is a neat concept and an interesting thought. The actual way these dark sides manifest is a bit bland, being focused mostly on general evil gurning and an obsession with Kes that twists the Doctor’s own genuine feelings for her into something more sinister. There was more subtlety to William Shatner’s Evil Kirk in ‘The Enemy Within’. But it does the job of providing some chilling moments, especially when B’Elanna finds herself at the mercy of the Evil Doctor.
One to avoid if you’re scared of: Doctors, creepy stalkers.
18. Discovery: season 1, episode 3 ‘Context Is For Kings’
This is only the third episode of Discovery, and the first to be set on the titular ship, so it’s our introduction to much of the crew and to the series in general. At this early point, it looked like Discovery was heading in a very dark and horror-tinged direction indeed. With Gabriel Lorca as Captain, Burnham still a prisoner, and Stamets at his frostiest, the series already promised to be ‘darker’ – and then we find out the grisly fate of Discovery’s sister ship’s crew, turned inside out, their bodies twisted and mangled. The rest of the series so far has gone to plenty of morally and emotionally dark places, but for sheer scares and perhaps a little queasiness, this is the one to watch.
One to avoid if you’re scared of: Gore, morally dubious Starfleet captains
17. The Original Series: season 1, episode 1 ‘The Man Trap’
Star Trek starts as it means to go on – the very first episode to air is one of the creepy ones (and the earlier pilots are both pretty unsettling as well). The main reason it’s remembered as a scary one is the great creature design on the Monster of the Week, the Salt Vampire. The combination of gaping, toothy mouth, drooping eyes and Yeti-like body is impressively inventive. But there’s an emotional core to this episode as well, as Dr McCoy’s ex turns out to have been killed by the creature long ago. Her husband’s willing acceptance of the creature that killed her as a replacement is probably the creepiest thing of all.
One to avoid if you’re scared of: Shapeshifters, the Yeti.
16. The Next Generation: season 7, episode 6 ‘Phantasms’
Another nightmare episode, but it’s not originality we’re giving points for here. The plot of this episode is fairly basic and the key concept of seeing nightmares is one we can see plenty of elsewhere – it’s not even the only ‘nightmare episode’ from The Next Generation. But the reason both appear on this list is because, while the concept may not be stunningly original, and the episodes may even be rather cheesy, the bizarre images we see in them are genuinely unnerving. The Troi-cake may be often mocked, but it really is a freaky image, iffy visual effects notwithstanding. Add to that Dr Crusher drinking from Riker’s head and a phone inside Data’s body, and you have a good set of weird images to freak yourself out with this Halloween.
One to avoid if you’re scared of: Being eaten, being drunk from.
15. Enterprise: season 3, episode 16 ‘Doctor’s Orders’
One of two episodes on this list directed by Voyager’s Roxann Dawson, who clearly has a good eye for a creepy set-up. The plot has something of a connection to Voyager as well, as it’s essentially a re-tread of the Voyager episode ‘One’; most of the crew are put to sleep for medical protection while one or two, immune, crew-members are left to roam the ship alone. The earlier episode featured a longer period of isolation and a more vulnerable crew-member (former Borg Seven of Nine, who had a terror of being alone), but this one just edged it onto the list thanks to a few details. It has some welcome comedy beats breaking up the repetitive nature of isolation (Phlox wandering around naked is a nice touch) and Phlox consciously refers to the situation as a ‘haunted house’ for a reason, as it deliberately draws on classic tropes like rattling chains, dark shadows, and strange noises. Also this one includes a cute dog. A spooky story can always be enhanced by throwing in a cute dog.
One to avoid if you’re scared of: Haunted houses (or spaceships), giant insects.
14. Deep Space Nine: season 3, episode 26 ‘The Adversary’
This was the third season finale, and it opens with Sisko recording “my final Commander’s log” – that’s because he’s been promoted to Captain, but it creates a sense of finality, of the closing of a door, from the start. It makes the subsequent paranoia-inducing hunt for an enemy who could be disguised as any member of the crew – a Changeling – even more tense. Odo says no Changeling would ever harm another, so you know what’s going to happen by the end of the episode, but it’s well made; claustrophobic, with echoes of The Thing and body snatcher themes (without the actual snatching). No one knows who to trust and everyone is getting trigger-happy – foreshadowing the increasing violence that would become a feature of the series as it moved towards a war storyline in the future. And Sisko has barely been Captain five minutes when he gets to play with the auto-destruct, as all Starfleet Captains love to do every now and again.
One to avoid if you’re scared of: Sleeper agents, clones.
13. Deep Space Nine: season 5, episode 5 ‘The Assignment’
A lot of the episodes on this list take a classic horror fantasy trope and give it a science-fiction mask – ghosts that are gaseous aliens, witches that are telepathically powerful aliens, vampires that are after salt rather than blood. This one is a science-fiction take on demon possession, as poor Chief O’Brien is told that his wife has been taken over by a malevolent entity, but he can’t tell anyone else without risking her life and his daughter’s. Key to the whole thing is a great performance from Rosalind Chao, whose manner and bearing through the whole thing is definitely that of a new character who is not Keiko.
One to avoid if you’re scared of: Demon possession.
12. Enterprise: season 2, episode 10 ‘Vanishing Point’
There are a number of Star Trek episodes where various crew-members think they’re dead and wandering the ship’s passageways as a ghost (and one slightly odd episode of Voyager, ‘Cathexis’, where Chakotay literally does so). Most focus on the impact of the apparent loss on the other crew, contemplations of the afterlife, and so on. In this episode, though, Hoshi first experiences unsettling body horror as birthmarks move and her translation skills fade, then seems to be becoming a ghost slowly, unable to touch things properly and even starting to vanish entirely. It’s far more spooky and freaky than the usual ‘out of phase’ storyline. And here’s an extra dose of horror – all this seemed to happen to Hoshi during the 8.3 seconds she was in the transporter buffer. So what exactly did Scotty go through when he ended up stuck in there for 80 years in The Next Generation’s ‘Relics’?!
One to avoid if you’re scared of: Turning invisible, matter transporters.
11. The Original Series: season 3, episode 4 ‘And The Children Shall Lead’
Before we get to the opening credits of this episode, we’ve already seen a group of children dance around happily singing a strange version of ‘Ring a Ring a Roses’ at the site of a mass adult suicide. Do you need to know more than that?! Later on, they all move round in a circle chanting a call to a ‘friendly angel’ which produces a green, translucent being wanting universal control (as usual) and they set about driving the crew of the Enterprise mad using bizarre hallucinations including premature ageing, planets that aren’t there, and so on. I mean, if that summary doesn’t creep you out, you’re either a sadistic small child or a power-mad translucent green alien yourself. As a bonus, it has a genuinely affecting ending, too, as the full horror of what happened to their parents hits the children.
One to avoid if you’re scared of: Creepy children, children in general.
10. Voyager: season 3, episode 15 ‘Coda’
This episode is another “I’m dead!” fakeout, in which a crew-member – in this case Captain Janeway – appears to have died and seems to be watching their friends mourn them as a ghost. This one has a couple of twists though. There’s a time loop element with Janeway experiencing repeated deaths of different kinds in different loops. And then, just to really freak us out, a sinister alien tries to convince Janeway to follow him to the afterlife, even implying that he is waiting at the point of death for her, and everyone else, whenever and wherever she eventually dies. It seems far more likely he’s just a creepy Delta Quadrant alien trying to harvest something, somehow (a soul eater? does he eat life force?) but it’s still a deeply disturbing concept.
One to avoid if you’re scared of: Death and dying.
9. The Next Generation: season 3, episode 26 ‘The Best Of Both Worlds, Pt 1’
The Borg were first introduced in the episode ‘Q Who’, and they were fairly terrifying then. Their total lack of interest in anything they don’t perceive to be a threat ironically makes them so much more frightening than they would be if they attacked others on sight, while their cybernetic implants and collective consciousness give them a ghoulish creepiness. But however terrifying they seemed at first, they became so much scarier again when their main method of conquering was introduced – assimilation. Even in this episode, there’s not a whisper of it for most of the story – until the captured Captain Picard turns to face Beverley (and the camera) to reveal a face full of Borg technology. “He is a Borg!” as Worf exclaims. On first viewing, with no idea it was coming, it was a serious shock, and seriously scary.
One to avoid if you’re scared of: Cyborgs, Oxo cubes.
8. Deep Space Nine: season 4, episode 24 ‘The Quickening’
We had to include this one, in which Dr Bashir desperately tries to help people suffering from ‘the Blight’, a fatal illness caused by a biological weapon long before the story starts. It’s not an infectious disease, but it is passed from mother to child through the generations, and society has completely reformed around it, developing a system of ritualised euthanasia as the only method they have for dealing with it. I trust there’s no need to spell out exactly what is so scary about this scenario. It’s also extremely depressing. There’s some hope at the end, for Ekoria’s baby at least, but it’s small comfort after the harrowing grimness of the rest of the episode. To be honest, we’re not sure we’d entirely recommend watching this episode right now, unless you’re in the mood for some serious wallowing. But it is definitely scary. Very, very scary.
One to avoid if you’re scared of: Biological weapons, plagues.
7. Enterprise: season 3, episode 5 ‘Impulse’
Often, the scariest or most impactful episodes have the shortest cold opens. This Enterprise episode drops us straight into the action with a screaming T’Pol brought into sickbay, clearly out of control – and cut to credits. Now that is the way to unsettle an audience from the start! Jolene Blalock puts in a great, unhinged performance and the shaky camerawork all adds to the feeling of horror, so by the time we flash back one day to find out what’s happened, we’re prepped for horror. The rest of the episode plays out in classic space horror movie style, all darkness and noises and flashing lights, everyone running around looking filthy and sweaty being chased by Vulcan zombies while poor T’Pol descends further and further into madness. A 45-minute mini horror movie.
One to avoid if you’re scared of: Your own strong emotions, zombies.
6. Deep Space Nine: season 5, episode 24 ‘Empok Nor’
This one is another horror movie in miniature. You know things are going to go seriously wrong when a handful of regular characters go on a mission with a collection of character who, if they were in The Original Series, would probably be wearing red shirts. This episode, in which our heroes go scavenging on Deep Space Nine’s abandoned sister station and discover some unhinged Cardassians, has got dark corridors, a diminishing cast, a regular character under the influence of psychotropic drugs becoming dangerous, and the odd jump scare. It gives Andrew Robinson as Garek an always welcome chance to play the more sinister side of the character, and keeps the tension running high throughout.
One to avoid if you’re scared of: Dark corridors, slasher movies.
5. The Original Series: season 2, episode 14: ‘Wolf in the Fold’
A number of original series episodes are scary in the wrong way, for the wrong reasons. Despite Star Trek’s overt efforts to combat sexism in its own way, it was still a deeply sexist show made in a sexist time, and could be outright misogynistic on occasion (the very last episode, ‘Turnabout Intruder’, is probably the worst offender). But ‘Wolf In The Fold’ blends the rather less enjoyable creepiness of women being objectified with some properly horrifying chills. It’s implied through much of the story that Scotty might be a serial killer, which is genuinely unsettling, as it plays into the very real fear that anyone around you, someone you feel you know well, could be hiding a dark secret. While the eventual reveal that he has somehow been possessed by Jack the Ripper (who was an alien life form possessing a human, of course) offers some comfort there, the idea that a Victorian serial killer entity has been travelling around killing women for centuries is certainly frightening.
One to avoid if you’re scared of: Serial killers, Scotty.
4. The Next Generation: season 6, episode 21 ‘Frame Of Mind’
Poor Riker. He’s just finished performing in a play in which he plays a man kept locked up, drugged, and experiencing a mental breakdown, and he gets abducted by aliens who keep him locked up, drug him, and force him to question what is or isn’t real, provoking a mental breakdown. What were the chances, eh?! Jumping between his usual role on the Enterprise and being a patient in a mental institution who has committed some horrible crime, it becomes increasingly difficult to work out what’s ‘real’, and in the end, just about none of what we saw was real at all – except for Riker’s very real imprisonment by a hostile alien. Jonathan Frakes puts in a wonderfully frazzled performance in an episode that will make your head spin, leaving the audience as confused as Riker is.
One to avoid if you’re scared of: Mental institutions, being imprisoned.
3. Voyager: season 4, episode 7 ‘Scientific Method’
This is the one where an alien race who keep themselves invisible use the Voyager crew as test subjects for their lab experiments. The initial mystery is intriguing, but it’s after the reveal that things get really alarming. What was a frustrating and extremely familiar medical problem for Janeway, recurrent headaches, becomes a terrifying visual as we see the aliens surrounding the oblivious Captain, sticking enormous needles into her brain. Then, in one of the more chilling and uncomfortable sequences of television you’re likely to see, Seven of Nine, the only person able to see them, must then ignore them completely while they probe her as she takes the turbolift. Luckily Janeway puts a stop to it by flying right at some binary pulsars, and these aliens are so scary that actually seems like a good idea.
One to avoid of you’re scared of: Scientists, needles.
2. The Next Generation: season 6, episode 5 ‘Schisms’
There’s a recurring theme to a lot of the scariest episodes in this list – body horror. It’s what steps the Borg up to becoming even more terrifying than they already were, it’s what makes ‘Scientific Method’ so incredibly chilling, and it’s a big part of what makes ‘Schisms’ one of Star Trek’s all-time most unsettling episodes. The revelation that Riker has had his limbs amputated and re-attached is simply horrifying. Combine that with a classic alien abduction story and the incredibly unsettling, insect-like clicking noise the abductors make, and you have a properly scary alien abduction horror story to rival The X-Files (one of the biggest shows on television at the time it aired).
One to avoid if you’re scared of: Alien abduction.
1. Voyager: season 2, episode 23 ‘The Thaw’
Ranking these episodes in pure terms of how freaking terrifying they are, this instalment easily comes out at number one. Coming out shortly before The Matrix, this episode features a similar premise, that if the brain is hooked up to a virtual environment, a lethal shock within the virtual world might kill the person. But it’s taken in a very different direction, for the friendly aliens who initially went into the virtual environment to while away a long time in stasis have been taken hostage by a virtual clown and his circus troupe, the manifestation of their fears run amok. So basically, they’re trapped in an unending nightmare, kept in a state of constant, perpetual fear by a garish collection of unnerving characters. The entire episode is one terrifying set-piece after another, with a fantastically energetic performance by Michael McKean as the Clown. It’s all so scary it’s downright uncomfortable. Thank goodness for Janeway’s last minute insight into what Fear really wants – to be conquered.
One to avoid if you’re scared of: Clowns.
The Original Series: season 3, episode 12 ‘The Empath’
A number of Star Trek episodes deal with torture, and we’ve tended to leave them off this list as they’re really more upsetting, disturbing, or tragic than chill-down-your-spine scary. This one is pretty freaky, though.
The Original Series: season 3, episode 7 ‘The Day Of The Dove’
Much of this episode is a fairly standard early Klingons episode, albeit with a mysterious glow cloud (all hail!) floating around and swords appearing out of thin air. But when Sulu tells Kirk that the dead brother Chekov has been talking about all episode long never existed, we realise something stranger is going on.
Voyager: season 4, episode 25 ‘One’
Pretty similar in concept and execution to both ‘Persistence of Vision’ and ‘Doctor’s Orders’ (and coming right between the two). Still a scary concept, though.
Discovery: season 2, episode 12 ‘Through the Valley of Shadows’
Pike’s willing acceptance of his fate – and the fact we know it’s accurate from The Original Series – is heroic, tragic, and chilling all in one.
Picard: season 1, episode 6 ‘The Impossible Box’
Think about what happens at this episode’s climax from Soji’s point of view, as the person she trusts the most reveals that she’s not even human and then tries to kill her, and recoil in horror.
Lower Decks: season 1, episode 1 ‘Second Contact’
As mentioned above, this episode features plenty of classic horror tropes including blood, guts, gore, vomit, zombies and a giant spider. Watch it for some light relief after you’ve worked your way through the rest of the list!
(Dis)-honourable mention: The Next Generation: season 7, episode 14 ‘Sub Rosa’, aka The One Where Bev Boinks A Ghost. It’s too ridiculous to be properly scary, but there is a half-decent ghost story buried in there somewhere.