WARNING: If you've not watched the latest episode of Ashes To Ashes, you really, really, really don't want to be reading this review.

Where do you start after an episode like that?

With the bullet removed from her brain in the ‘real world’, we see Alex kicking off this week in high spirits. But her cheery demeanour about going home serves as a portent of doom for the rest of the episode, as things go from bad to worse. And what initially seems like a basic drug bust provides a whole lot more, as Ashes To Ashes delivers, by far, its darkest episode to date.

Busting a drug dealer on a construction site, Gene and the rest of the team find a buried body encrusted in concrete, leading to a murder investigation involving a dodgy site manager, Polish labourers and a police officer who should prove very familiar to viewers of the series.

It’s hard to review this episode without giving away too many spoilers. Again, we repeat: for those who have yet to see the episode stop reading now... really, it will spoil things too much if you carry on. There was a murder, they find the bad guys, Alex doesn’t wake up yet and Gene kicks in some nonces. That’s all you need to know. Pop over to the 100 movie clichés article, then watch the episode on iPlayer over lunch then come back.

Right... now they've gone we can get onto the juicy stuff.

It seems that in this 1980s reality, two versions of yourself can exist simultaneously, as we are introduced to PC Summers, a ‘clean’ cop, who Gene entrusts with assisting the team take down of Michael Lafferty. Lafferty is a construction site manager who it seems is using cheap European labour, avoiding paying taxes and with friends apparently in very high places. With Summers and Lafferty at odds with their story, Gene feels he should trust the young PC, whereas Alex is more inclined to believe Rafferty, as it seems that Summers is indeed the young version of the corrupt policeman who knows so much about Alex’s real predicament.

With the scene set, things take a much darker tone as we get not one, but two, big ‘reveals’, both of which are very shocking and frankly fantastically played out.

First of all (and for those people who have kept reading and not seen the show  ... really this is your last chance!) Alex is confronted by older Summers who asks her for a meeting. Summers also invites the younger version of himself, promptly shooting him dead. Explaining to Alex that you can ‘change things in this world’, his casual mockery of her when she expects him to disappear or blow up or create a ‘negative reality inversion’ or something by killing his younger self, shows he knows a lot more about this reality than she does. This makes him even more dangerous than first thought.

So with a dead policeman at her feet and no fingerprints on the gun (apart from Summers), Alex, in sheer panic ,does the unthinkable, burying the body in concrete on the building site, mirroring the murder at the beginning of the episode.

Linking in with this, Ray, Chris and Gene are following leads to the murder, trying as best they can to link evidence to Lafferty. They eventually find a piece of paper that has co-ordinates on it in Polish, something that causes a lot of problems as during the investigation, this vital piece of evidence disappears.

With this vital clue having been misplaced, Gene finally realises he has a mole in his operation and that problems with evidence disappearing and mismanagement of paperwork are not errors after all, but really a slow methodical calculated attempt to tamper with cases and evidence. In an elaborate plan, Gene sets everyone at the station up, heightening the tension and accusations until the team reach boiling point, blowing up in Luigi’s after days of secrets and subterfuge.

With everyone at each other's throats Genes’ ‘Who can you trust?’ plan springs into action, and discovers the culprit for all the misplaced and disappearing evidence. It seems there is indeed a mole in the station, one desperate for money for his up and coming wedding. Yep, in a complete shock it seems that Chris has been taking back-handers from an unknown source to misplace evidence.

In a scene that shows you just how good the actors are in this show, Marshall Lancaster gives the performance of the week as he slowly breaks down and reveals all to Gene, who sits there stoic in his judgement (and what a steady, measured performance from Phillip Glenister, too) as Chris explains his need for money to impress Shaz. He reveals all about his little jobs here and there, and how the pressure has been building up as the work he has to do from his unknown employer has become darker and much more corrupt.

Acting as judge for Chris, Gene does not accept his resignation, leaving him to feel the wrath of friends and peers as he is forced to go back to work with the friends he has betrayed, living with the guilt. Again this superb piece of plotting and acting is really bought home as Ray, Shaz and the rest of the team all judge Chris, leaving him alone in the office to suffer. It's a devastating and haunting scene, stunningly well realised.

With this confession finally off his shoulders, the team are in a better position to find out what is actually going on, uncovering Rafferty’s rackets (stolen weapons) straight away and blowing apart part of a bigger operation, which is seems may well be ‘Operation Rose’.

With the promo for next week it seems that Chris might well be back on the path of redemption as his anonymous paymasters ask him to take part in a big operation, that may lead the team to bigger things and get Alex that little bit closer to going home.

Overall, a superb episode all round, with so much packed into an hour and so many strong performances. And the culmination of Chris’s confession and the way it's treated by rest of the team is one of the strongest bits of drama from the entire series. The series finale is going to have to go some to beat it.

Check out our review of episode 6 here.