A sophisticated jewel thief tries to prove himself innocent of a string of cop murders.

An apparent suicide by a rich woman leads her nurse and a policeman to an insurance scam.

A decoding expert tangles with enemy spies.

Epidemiologist Cliff Claybourne falls in love with Rita Wilson in a gambling house. They want to marry but Cliff's brother is convinced Rita is no good and forces Cliff to fulfill his agreement to do research in Africa in exchange for paying gambling debt. Rita, Cliff and brother are furious with each other, but Rita and Cliff are still in love.

A reporter covering a murder trial guesses that the murderer of a ruthless businessman is her ex-fiancé and persuades him to confess and clear the innocent man on trial.

During WWI pretty German master spy Helene von Lorbeer is sent undercover to London to live with the family of a high-placed British official where she is to rendezvous with the butler Valdar, also a spy, and help him transmit secret war plans back to Germany.

The invention of a machine that can cause remote explosions brings the attention of Scotland Yard and Bulldog Drummond.