Intending to shortly wind down the company, Calderwood has converted its funds into diamonds, which will be shared equally between himself and his partners John Crewe and Monet, and company secretary Diana Marsh, none of whom trust each other or Calderwood.

Detective Superintendent Meredith of Scotland Yard is suspicious of the company's activities, but is unable to persuade any of its blackmail victims to help the police.

Diana and Stafford have fallen in love, and as they are about to flee the country, Meredith arrests them for plotting the murders.

The plot's intricacies are carried with a flourish and the characters' ingenious capacity for double-crossing is enjoyably portrayed by a strong cast.

As the persistent cop, Bernard Lee is so good he almost upsets the balance of this essentially modest entertainment.