Collision (TV series)

DI John Tolin returns from leave to investigate a traffic collision where two people have died. His superiors have concerns as the two traffic officers were in a high-speed chase at the time of the collision and the department is now being sued by Alice Jackson's family. Jackson was in the car being pursued, and was killed, and the family thinks racial profiling might be involved in choosing her car to pursue. All of the victims of the crash and the first layer of their back stories are introduced, but nothing is as it first seems. There is a strong hint that Tolin's leave was due to some sort of tragedy, and that it might involve events similar to this investigation. The episode ends with Tolin, in his office, imagining the crash itself.

DI Tolin goes to the scene, where the office in charge of the investigation is Insp. Ann Stallwood. Tolin and Stallwood had a relationship a year earlier, which went sour and seems related to events linked to Tolin's having taken leave. The backstory of Danny Rampton, driver of a white van, indicates he is transporting something illegal, and dealing with shady characters. A PC at the crash scene mentions Jackson's car window being rolled down while the air conditioning was on, leading Tolin to deduce that Jackson was smoking pot, as was her boyfriend, the driver. Jackson's father drops the lawsuit, pleasing the police administration. They want to reassign him to a new case. Tolin, though, wants to investigate other matters and tie up loose ends. It is also revealed that Tolin has a daughter in a wheelchair.

The driver of a white van that crashed, Danny Rampton, who ran from the scene, is found to be trafficking illegal immigrants. The one in his van, Tsegga, is found a week later, dead, by police forensics working on the vehicles. There is a back story about him, his journey, and his wife, who is in London and waiting for him. Karen Donnelly, the personal secretary at a large chemical company, had stolen documents from her boss revealing exploitation of East Africa and dangerous pesticide use just before being involved in the crash. With the help of unknown people she checks out of the hospital and is later found in the bathtub of her apartment, an apparent suicide. Tolin is not so sure. Jane Tarrant, a waitress at a rest stop near the accident, begins a dalliance with a rich businessman Richard Reeves.

It is revealed that a drunk driver killed Tolin's wife a year before and put his daughter in a wheelchair. The driver, Henry, is released from prison and seeks forgiveness from Tolin. Tolin beats the man up when he won't leave Tolin's home. In a conversation with his daughter about the incident it is revealed that Tolin was having an affair with Stallwood at the time. Sandra Rampton, Danny's sister-in-law who sees Danny as a screw up jeopardising her family, arranges for Danny to get a passport so he can disappear, but the traffickers kill him instead. It is implied that Sandra knew that this, and not the passport, would be the result. Karen Donnelly had stolen documents for a reporter calling himself James Taylor, but all might not be as it seems. Jane Tarrant's relationship with Richard Reeves gets more serious.

Joyce Thompson is the mother of Christine Edwards. Thompson died while in a car with Brian Edwards, Christine's husband. Her death puts a strain on the marriage. Mrs. Edwards blames him, and it is slowly revealed how much Mr. Edwards hated his mother-in-law and how she treated Ms. Edwards. Finally, he admits that, after the crash, Mrs. Thompson was alive but her nagging voice pushed him to slam her head against the dashboard repeatedly. Jane Tarrant and Richard Reeves decide to leave their partners and travel to Europe, but Reeves' wife shows up at the station instead to tell Tarrant that her husband has made promises before but will never leave; he's a coward. Tarrant screws up her courage and goes anyway, living her dream. Tolin finds a thumb drive on Karen Donnelly's keychain that contain the stolen documents. After revealing the man Donnelly thought was reporter James Taylor is not, Tolin gives the documents to the real Guardian reporter the man was impersonating to give Donnelly's death—and the risk she took to reveal injustice—meaning. Previously, throughout, it's hinted at that Sidney Norris, the piano instructor and main cause of the accident, might be a paedophile. (However this is just another red herring, as ...) Tolin and Stallwood track down a suspicious friend of Norris' only to discover their "secret" is that they have bootleg Star Trek episodes, which explains the amount of time Norris spent on his computer. Tolin and Stallwood reconcile, with Tolin finally coming to peace with his wife's death. In the end, Stallwood realises Norris was distracted by a wasp, causing the collision and consequent entire change in the sequence of events. The last scene is an alternative timeline 'what if' : showing that if Tarrant, back at the roadside diner, had squashed the wasp (as almost seen in the first episode) and the entire crash had been avoided, as they all continued on their 'pre-existing' path...