The Surprising Thing That The Flight Attendant and Sherlock Have in Common

Cassie’s evolving mind palace in the HBO Max mystery series takes a page from the Great Detective’s deductive tool.

Kaley Cuoco in The Flight Attendant season 2
Photo: Lara Solanki | HBOMax

This article contains spoilers for The Flight Attendant seasons 1 and 2 and Sherlock.

The best mind palaces—a mnemonic device in which you create a space to store memories, information, and other subconscious scraps—are those built to resemble someplace familiar or personal. That makes it incredibly ironic, then, that all of Cassie Bowden’s (Kaley Cuoco) mind palaces are hotels. The internationally jetsetting flight attendant and (very) amateur detective at the heart of HBO Max’s The Flight Attendant spent season 1 trapped in a mental recreation of the lavish Bangkok hotel suite in which she woke to find her dead one-night-stand Alex (Michiel Huisman) with his throat slit. Though she solved his murder, season 2 catapults a one-year-sober Cassie back into a new mind palace: the Berlin hotel bar where yet another man she interacted with (platonically this time!) is dead.

But instead of that man’s ghost, it’s herself behind the bar: Bangkok Cassie, decked out in her glittery gold party dress. There’s also Bender Cassie, raccoon-eyed and sullen and cruel. And Perfect Cassie, the persona she could be if she leaned into her (boring) new life a bit more: promoted at Imperial Atlantic, rocking a huge engagement ring, barely holding it together. And—Young Cassie, the child who was her dad’s drinking buddy, the girl who ran toward a plane crash because she loved being in the middle of drama no matter who got hurt.

Season 2’s mind palace is even more surreal than its predecessor, populating the gold-plated hotel lobby with props from her waking life: Her brother Davey’s endearing yet obnoxious “Easy Does It!” teddy bear to mark one year of sobriety; a massive model of an old house that her younger self painstakingly builds despite knowing it’s as flimsy as a house of cards; synchronized swimmers performing trippy choreography; a giant martini glass overflowing with the drink that could make all of her stresses melt away.

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Because the urge to drink is always with her. And this time, the murder is incidental; the true mystery is, who is trying to frame Cassie?

Whereas season 1 Cassie—a hot-mess, barely-functioning alcoholic—incriminated herself left right and center, season 2 Cassie is trying her damnedest not to look guilty of yet another murder. Unfortunately, despite moving to Los Angeles and marking a year of sobriety with AA, her old temptations to chase the adrenaline high of international conspiracies means she has to clear her name again. So after closing the door on her mind palace and throwing away the key, Cassie needs to find her way back to the place that no version of her believes she belongs in in the first place.

Let’s be real, when you think mind palace, the immediate mental association is the Great Detective himself, Sherlock Holmes, as embodied by Benedict Cumberbatch in the BBC’s Sherlock. And Holmes’ precisely honed mental device for solving mysteries is the kind of tool that someone like Cassie—selfish, flighty, a liar and manipulator—should have no business using.

It’s not as if Cassie coolly accesses it like a computer program, like Sherlock in the series 2 episode “The Hounds of Baskerville.” The mystery series’ first depiction of the mind palace resembles a search engine algorithm whirring away in real time, as the detective systematically works through what association the word “hound” could be pinging within him. We watch him spin, Tony Stark-style, through encyclopedic entries and even a clip of Elvis singing “Hound Dog” until he lands on the acronym H.O.U.N.D., which points to an abandoned CIA project that ultimately explains the hallucinations wrapped up in that episode’s mystery.

See? All very neat and civilized. By contrast, a panic attack propels Cassie out of reality and back to that hotel room and Alex’s chatty corpse. The reminder of all that blood has her rushing to defend herself: “I’m not that kind of drunk!” The life of the party, she insists, not the cause of death.

But, he points out, she also didn’t notice that someone murdered him in his sleep. “So, you’re also a blackout drunk.” A blackout drunk who has no solid alibi nor any useful memories of the night before… until she begins really looking around the space in which she’s trapped herself. Cassie mentally rifles through his suitcase and recalls details she must have barely glimpsed between bouts of sex and rounds of drinks. But these shreds of potential evidence aren’t nearly enough to counter the situation outside of her head: she cleaned up the crime scene and then fled, both of which look incredibly guilty.

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And each time she returns to the mind palace, it’s in increasing states of panic, shame, and/or drunken episodes. Cassie is dissociating from reality hard, with no control over when she drops back into this room for half-answers.

Sherlock utilizes his mind palace at a party—specifically, John Watson’s (Martin Freeman) wedding in the series 2 episode “The Sign of Three”—but very much keeps his cool. By this point, the mind palace has evolved from a mental database of word associations to an actual space: a courthouse populated with his impressions of the wedding guests, a.k.a. suspects. As he interrogates them, while dealing with his brother Mycroft (Mark Gatiss) condescending to him about coincidences from the judge’s seat, Sherlock must work with just the stories and anecdotes passed around with the hors d’oeuvres during cocktail hour.

That’s what’s tricky about a mind palace: The information all originates with the person who built it. That’s all well and good when working within a limited library of one’s own research, but much thornier when it comes to half-formed impressions of real people. Cassie’s Alex isn’t the entirety of Alex Sokolov, only her jumbled memories of and assumptions about a man she spent a drunken layover with. Until, that is, she breaks into his apartment. 

“Other People’s Houses,” the midseason turning point of season 1, expands the scale of Cassie’s mind palace by transplanting a floorplan of Alex’s even more sumptuous digs inside of the opulent suite, while in real life Cassie is going through what might as well be a stranger’s home. Nothing she finds matches the charming man from Bangkok, and so begin the judgments and even suspicions that maybe he deserved to get murdered.

Cassie’s Alex takes exception to her exhuming a life he’s not alive to provide context for, but she doesn’t listen to him until, in one of the series’ best moments, he turns the spotlight on her. Suddenly the mind palace’s windows looking out onto Bangkok are instead dioramas of Cassie’s apartment, from the mess of a frequent traveler to the damning empty bottles of an alcoholic. Because this Alex has all of the ammunition needed to discredit Cassie—after all, he’s pulling it all from her own head. She tries to take control of the evolving mind palace by erecting a mountain of vodka bottles, mocking the pity and disgust she imagines he feels for her as a stereotypical alcoholic, but this overwrought display only reveals the depths of her own self-loathing.

This sequence is messy and cringeworthy and painful to watch. It possesses nothing of the restraint nor subtle symbolism we observe in the final evolution of Sherlock’s mind palace in the series 3 finale “His Last Vow”: a winding staircase with floors and rooms expanding outward. We don’t even know the place exists in this form until John’s wife Mary Morstan (Amanda Abbington) shoots him and he retreats inward to stay alive. This time, instead of conjuring up words and phrases to check against his own knowledge, Sherlock’s subconscious manifests key people from his life, including Molly Hooper (Louise Brealy), who talks him through exit wounds and which direction to fall to prevent himself from bleeding out. There’s also a downstairs run-in with Jim Moriarity (Andrew Scott) that ultimately pushes Sherlock back to life to save John.

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Because a mind palace is not fully functional unless it’s personal. But “personal” doesn’t just mean dropping in avatars like playing The Sims; it must tap into actual life skills. Flight attendants’ myriad job responsibilities include customer service, which means they must be attuned to passengers’ minute needs—it’s the little details that make the flight unmemorable in its pleasantness, as opposed to awful and unforgettable. They’re also used to being stuck in a metal tube tens of thousands of miles in the air, which means they’ve perfected how to stay cool in situations ranging from actual aviation emergencies to spending twelve-hour-long flights with asshole passengers. Someone like Cassie is a pro within claustrophobic situations.

And Cassie is sharp. It just takes us and her so long to recognize it, because of how early in her life her father dulled her senses and impulses with alcohol. He taught her to be the “fun” one instead of the smart one. He buried her under layers of abuse and cruelty and self-loathing so that as she’s building up who Alex is, she’s simultaneously stripping Cassie down to her true self.

Sherlock’s mind palace is a dreamscape which he can enter and leave as if lucid dreaming, but Cassie’s is a nightmare in which she’s trapped—and that’s what elevates her mind palace over the Great Detective’s. Even despite the personal touches and associations, his still more resembles a computer simulation; hers is an actual memory bank. That includes confronting her childhood memories of “fun” with her dad, which were really getting drunk with him and torturing her brother Davey for being gay, ultimately not taking any responsibility for her cruelty, until the drunk driving accident that kills her dad.

Cassie’s mind palace is a self-made labyrinth with no thread to mark the way. It’s a Pandora’s Box that gets upended. And she has to do all of this in front of a version of the man she might have loved but will never get the chance to. And she still figures out who murdered him, even while unraveling her own blackout memories of her past.

After the events of “His Last Vow,” Sherlock neatly shuts the door on the mind palace until the next time Holmes needs to enter it. Whatever brief emotional resonance existed gets packed up, too. But The Flight Attendant heightens the personal stakes of Cassie’s mind palace by making her believe that this is a crutch tied to her alcoholism; after all, she mostly accesses it as her worst self. Endeavoring toward sobriety means Cassie literally destroys the path back there, which is why she needs an external motivator in season 2: the lingering tinnitus from the car explosion in Berlin. Every time it’s triggered, she finds herself back in that bar, where she and the deceased CIA mark had shared a brief camaraderie about their respective sobriety and how it necessitated sacrificing the “fun” or “exciting” versions of their lives.

Cassie didn’t choose a room—symbolizing no-strings-attached sex, or the allure of dressing up as a different person, but all in private—this time, she chose a public bar with its temptations right on display. And while she initially resists the drinks that her party girl self keeps mixing for her, citing her hard-earned year of sobriety, even that turns out to be false. In “Drowning Women,” Cassie’s other selves force her to admit the lie she’s been keeping for the past 365 days: that she slipped in her sobriety six months in, while she was still in New York, and fled her old life—just like Bangkok—rather than pick herself back up. That she’s been lying to everyone but especially herself about how “well” she’s doing, when she’s actually still at square one.

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The layout may have changed, but yet again Cassie’s mind palace is an arena for excavating uncomfortable truths. Instead of worrying about what a dream lover will think of her should he learn the truth, Cassie must confront her own self-disgust with the revelation that she never actually went through the changes she claimed. We never witnessed this level of self-awareness from Sherlock, despite his own addictions. That’s where The Flight Attendant elevates the notion of a mind palace, and promises to unlock greater mysteries than murder—namely, can someone like Cassie find a version of herself that she thinks deserves to live?

As Cassie is learning, the answers might not be behind a hotel bar, but it’s a good thing she found her way back to her mind palace—one day at a time.