Wikipedia anthony horowitz biography

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.