The coppers find a murdered man called Danny who was secretly informing the police. Sam is angry that Gene didn’t offer him protection in return. Frank later explains that Gene must be exposed for his criminal negligence, prompting Sam to explain about what happened with Danny. Then, Frank promises to bring Sam home once he has the necessary evidence and tape recordings.
Annie hears from Sam that he is going far away and wants to spend more time with her. Before they can speak further, a suspect is brought in for interrogation in the store rooms. Sam has hidden a tape recorder and it captures Gene and Ray brutally treating the man in order to gain answers. The methods work and the name Leslie Johns is supplied.
That night, Annie arrives at Sam’s flat for a word. After a heart to heart, Sam asks for one night together with her, but Annie rejects the short term proposition and leaves. He then sees the demonic Test Card girl enter his flat and suggest that he’s being operated on.
Gene Hunt plans an undercover operation to arrest Johns and an armed gang planning to stage a heist on a train carrying wages. Sam believes that without trained firearms experts involved the officers are being placed in unnecessary danger. Gene then meets Johns, using a false identity, and ensures that he is part of the armed gang. After this meeting Gene plans the operation and informs Sam, Annie, Ray and Chris that they are also to go undercover posing as the train’s staff. Although Sam is still convinced that the operation is risky and irrational, there is a telling moment where Gene Hunt defends his actions saying "I know we're dealing with a cop killer, but I have a responsibility to this city, and I will move heaven and earth to stop this man, now he doesn't play by any rules so neither should we." Sam then looks at Gene with a pained expression, realising for the first time just how difficult he will find it to expose him. Despite their differing methods of policing, it appears as if Sam recognises and respects Gene's simple honesty and fierce sense of duty in his work.
Sam meets Frank to inform him of the latest developments and evidence. He asks to return home, but Frank says he must stay on as part of an anti-corruption unit. Sam then starts making references to the coma and the brain surgery in the future, but Frank is dumbfounded. Sam is startled to learn he was in a crash several months ago before he went undercover and suffers from amnesia, with Frank listing the symptoms of hearing doctors’ voices.
The pair then visit a cemetery with tombstones of Sam’s dead parents, who have the surname Williams. Next to their graves are tombstones bearing the name Tyler, which is where Frank says he took his undercover name from. Shortly afterwards, Frank gives Sam a radio with which to contact him for backup during the train operation.
Nelson the barman then tells Sam that he is only alive when he can feel. The policeman later gives Annie a big hug and confesses that he was always going to leave and that he is working undercover for Morgan to gather evidence against Hunt. Chris and Ray walk in and Sam also tells them the truth about his links with Hyde. They are not pleased, despite Sam’s protestations that he wants to save their lives. Feeling cheated, Annie slaps Sam hard across the face.
Despite the friction, the team goes ahead with the mission as Gene has already gone undercover. When their train is being robbed, sounds from Sam’s police radio given to him by Morgan alert the crooks to the deception. As shots are fired, Gene breaks his cover to join his colleagues in the shootout. Sam radios Morgan for backup but none arrives. Promising that he will return, Sam makes a break for it and bumps into Morgan at the end of the train tunnel who tells him there is no backup and is happy to let the officers die to prove a point.
A bright, white light appears at the tunnel as Sam’s colleagues make a run for it and are shot down one by one screaming for his help. Sam follows the light and wakes up on a hospital bed to see surgeon Morgan’s face. His mother is sat silently at his bedside. Later, as Sam leaves the hospital, we see that he has been in the Hyde Ward, Room 2612: a reference to the place and phone number Sam had been contacting Morgan on. There are no jubilant friends or colleagues, or even his girlfriend, joyously present at his return from a coma.
Back in the present day, Sam rejoins the police force and undergoes psychiatric evaluation. He also visits his mother, explaining to her that in some ways he felt more alive in his coma than he’d ever been before. The promise he made to Annie in the train that he’d return starts to haunt him.
At a police meeting, Sam feels nothing. He has no opinion when asked and cannot feel that he was cutting his hand inadvertently. He slips off to the top of the building, alone, and surveys the landscape. He walks, then runs towards the edge and leaps off…
Sam then returns to 1973 and shoots Leslie Johns in the train tunnel before he can put a bullet into the wounded Hunt. Now back on good terms with his colleagues and enjoying a drinking session down the pub, Sam slips outside for some alone time with Annie, where he asks her what he should do. She says: "Stay here. Forever." They kiss. Gene interrupts them by pulling up in his Ford Cortina with Ray and Chris to inform them that a robbery is in progress and they must go. The radio on the car has a surgeon’s voice saying that "he’s slipping away from us", but Sam switches channels. The car speeds away into the distance as the banter continues between the pair, David Bowie’s ‘Life On Mars’ plays on the radio and a group of children run out of a backyard gate; the Test Card girl is among them. She stops, goes up to the camera and reaches out to turn the television off...
Metropolitan Accountability and Reconciliation Strategy