“At the end of the day, shut them away. Lock the drawer. You have to accept that you’re two people.”

Sergeant Johnson (Sean Connery) is a big, bruising, old-school copper. The funky newtown in which he works is being terrorised by a child murderer – three children have already died and the police have no idea who they are looking for. As the police watch frantic parents picking up their children from outside school, a little girl called Janie ignores the warnings and goes off on her own. A woman sees her talking to a man in the distance, and the next thing we know, Janie has been reported missing. The police immediately start a torchlight search across the common, and (surprisingly, to this jaded reviewer) Janie is found, abused but alive, by Johnson. Now things are personal for the Sergeant, and when a suspect is found and brought in, the angry Sergeant asks to be in on the interview.

The officer conducting the case, Cameron (Peter Bowles) is a modern (for 1973) policeman, and wants to let the suspect “sweat” for a while. But sensing an opportunity going to waste, Johnson manages to get time on his own with the man he is convinced is a child murderer. The burly policeman snaps and starts beating the suspect, who, covered in blood, refuses to stop laughing. By the time Johnson has finished, the suspect is nearly dead.

This is the offence that gives the film its title, seen in flash-forward at the beginning of the movie, as in silent slow motion the police officers outside the interview room realise that something is wrong and rush to stop the beating.

Johnson is immediately suspended, and as he drives home, visions of dead people crowd into his vision – a hanging corpse, a naked woman tied to a bed, a child dead in a cot, a woman lying in bed with a gaping gunshot wound. At home he cracks and tells his wife of all the death he has seen during his career, downing scotch after scotch as he does so. There is a knock at the door and Cameron and another officer enter – the suspect has died, and Johnson must come back to the station.

The police officer who has dedicated his life to solving crime is now a murderer, and Detective Superintendent Cartwright (Trevor Howard) arrives to conduct the interview. Cartwright is another old school policeman, well aware of how the job affects long-timers like Johnson. Years of thinking like a killer have taken their toll, and Johnson has even begun to fantasise that it was him who was responsible for the attack on Janie (“What’s happening to me?”). As battle between the two heavyweights ensues, Cartwright tells him: “At the end of the day, shut them away. Lock the drawer. You have to accept that you’re two people.”

But by the end of the interview, the Superintendent, who seemed quite sympathetic to Johnson’s predicament at the beginning, has made his feelings quite clear: “It makes me sick, Johnson, what you did. What you are turns my stomach.”

As you can tell, the film’s fractured timeline allows viewer perceptions to change, and then change again, as more information is made available. But it’s not just about the funky visuals (much of the flashbacks are obscured by a strange white orb, which turns out to be the lightbulb which oversees the whole attack) or the powerhouse performances (Ian Bannen as suspect Kenneth Baxter manages to put in a twitchy, seedy performance which, even in the brief moments he’s allowed on-screen, manages to steal the film from his more heavyweight colleagues).

The film is also a pin sharp document of the times – showing the groovy 60s turning into the grim 70s, with Sergeant Johnson an anachronism no longer wanted in the Force, an out-of-date thief-taker who looks hopelessly out of place in the gleaming new (half finished) police station where the bulk of the action takes place.