Waterloo (1)

Boyd is being promoted, which everyone on the team recognises as the worst news possible. The offer is a desk job, and the threat behind it is just as blunt: object, and his unorthodox methods get aired in public. But before he shuffles off to push paperwork, he vows to take one last case. Sixteen homeless teenage boys disappeared from Waterloo Bridge between 1979 and 1982, vanishing at three monthly intervals as if on a timetable.

Dennis Grant, a kindly vicar who had sheltered the boys, puts him in touch with Tony Nicholson, the only policeman at the time who seemed to care, now a high-ranking officer. Nicholson's old reports on the disappearances have mysteriously gone missing, which is the kind of coincidence this show has learned to distrust. The trail leads to a disused pub where the boys were taken and murdered by a sadist imitating the American serial killer Henry Holmes. Worse, the gun that killed them is the same weapon that shot dead Stanley Heath, a disgraced officer whose murder was never solved.

Then the case starts biting its own tail. Sarah Cavendish confesses that she complained about Boyd before going to see Nicholson, a man she now suspects deeply. It is a small, contrite admission, and it lands at the worst possible moment. After she spies on him talking to an elderly man, Boyd captures her at gunpoint.

Barbara Machin and Ed Whitmore wrote it, with Andy Hay directing. Trevor Eve's Boyd, Sue Johnston's Grace, Tara Fitzgerald's Eve, Wil Johnson's Jordan and Eva Birthistle's Cavendish are joined by Lauren Taylor as Cathy Nicholson, Ben Adams as PC Daniel Edgerton, Howard Coggins as Stanley Heath, Elizabeth Rider as DCC Maureen Smith and Robert Morgan as Ken Deighton.

The mystery is thirty years old and the players have aged into rank. Waterloo Bridge, it seems, keeps its own accounts.