A small time diamond merchant jumps at the chance to supervise the purchase and cutting of a large first class diamond. But when the diamond is stolen from him, he is blackmailed into pulling off a major heist at the Diamond Exchange, located at 11 Harrowhouse.
| Actor | Role |
|---|---|
 Charles GrodinHoward R. Chesser | Howard R. Chesser |
 Candice BergenMaren Shirell | Maren Shirell |
 James MasonCharles D. Watts | Charles D. Watts |
 Trevor HowardClyde Massey | Clyde Massey |
 John GielgudMeecham | Meecham |
 Helen CherryLady Anne Bolding | Lady Anne Bolding |
 Peter VaughanCoglin | Coglin |
 Cyril ShapsWildenstein | Wildenstein |
 Leon GreeneMax Toland | Max Toland |
 Jack WatsonMiller | Miller |
 Jack WatlingFitzmaurice | Fitzmaurice |
 Clive MortonSir Harold | Sir Harold |
 Larry CrossWhitman | Whitman |
 Glynn EdwardsFirst Guard | First Guard |
 John BindonSecond Guard | Second Guard |
| JJoe PowellHickey | Hickey |
| MMichael GoverDoctor | Doctor |
 Michael HawkinsPatient | Patient |
| PPatricia MichaelStewardess | Stewardess |