Polish aristocrat Leo Hagen lives with his wife, Christina, in an apartment in London. When Paula, the maid, catches Christina kissing Sir Harold Trevitt, their neighbor and a prominent Member of Parliament, she threatens to tell the jealous husband unless Sir Harold gives her £5,000. Private detective John Durran is hired by Sir Harold to investigate the maid, but the detective finds both Paula and Leo dead. Inspector Waveney of Scotland Yard becomes involved with the case and eventually proves Sir Harold to be the killer, and Christina is revealed to have conspired with her husband and Paula in the blackmail plot.