A lawyer receives a note telling him that he'll be dead in 48 hours - and Scotland Yard must work fast to uncover the serial killer known as 'The Ringer'.
| Actor | Role |
|---|---|
 Patrick BarrDet. Insp. Alan Wembury | Det. Insp. Alan Wembury |
 Alexander KnoxDr Anthony Lomond | Dr Anthony Lomond |
 Wilfrid LawsonMaurice Meister | Maurice Meister |
 Sonnie HaleSamuel Cuthbert 'Sam' Hackett | Samuel Cuthbert 'Sam' Hackett |
 Louise HenryCora Ann Milton | Cora Ann Milton |
 John LongdenInspector Bliss | Inspector Bliss |
 Patricia RocMary Lenley | Mary Lenley |
| PPeter CroftJohn Lenley | John Lenley |
 Arthur HamblingDet. Sgt. Richards | Det. Sgt. Richards |
 George MerrittPolice Station Sergeant | Police Station Sergeant |
 John TurnbullPrison Governor | Prison Governor |
 Charles EatonCol. Walford | Col. Walford |
 Cameron HallDrunken Scotsman (uncredited) | Drunken Scotsman (uncredited) |