A frightened woman is murdered in the London apartment of a well-known novelist named Henry Leroux. The police arrest Leroux's butler, but he escapes and runs off to a mysterious opium den, the lair of a drug dealer named Mister King. Gaston Max, a detective from Paris, arrives in London to investigate the drug trafficking. Although the police take down the gang, Mr. King escapes and manages to keep his true identity a secret.

Poisoner's victim turns tables.

'1765. Judge sentences highwayman to die, then finds he is his son.' (British Film Catalogue)

'France, 1918. Armistice saves girl and pilot from death, but not Canadian agent.' (British Film Catalogue)

'Girl reporter and insane fiancé join pirate's descendant in treasure hunt.' (British Film Catalogue)

In the Canadian Northwest, Royal Mounted Sergeant Tom Redding courts Jen Galbraith. Jen dislikes her brother Val’s friend Pierre, calling him "The Devil". Val takes offense when an Indian states his love for Jen, killing him. When Tom stops to visit Jen enroute to deliver secret orders to Fort Desire Pierre drugs the Mountie's coffee because he fears he carries a warrant for Val’s arrest. So, he does and after Val is arrested Jen and Pierre help him escape. An enemy tries to thwart them, but fate intervenes, and Pierre and Jen finally acknowledge their love for each other.

In the Jacobite Rising of 1745, the Young Pretender Bonnie Prince Charlie leads an insurrection to overthrow the Protestant House of Hanover and restore his family, the Catholic branch of the House of Stuart, to the British throne.

In India an engineer blackmails a girl over her gambling brother.

JP Paul Machin poses as a fugitive along the Cornish coast to gain the trust of a local smuggling ring. As he integrates into their world, he works to identify the leader and bring the group to justice.

A British submarine on patrol is accidentally rammed by a merchant ship, that tears a big hole in in sub which sinks trapping the crew.