When a corpse is found in the Thames, the only clue is that the dead man was killed by a karate or judo expert.
John Bentley
as Superintendent Wills
Patrick Allen
as Dr. Nelson Pollard
Jacqueline Ellis
as Elsa Marlowe
Wilfrid Brambell
as Lock-Keeper
John Glyn-Jones
as Dr. Maurice Tarn
Jane Murdoch
as Honeymoon Wife
