London. A mysterious serial killer brutally murders young blond women by stalking them in the night fog. One foggy, sinister night, a young man who claims his name is Jonathan Drew arrives at the guest house run by the Bunting family and rents a room.
Two thieves, the Blackbird and West End Bertie, fall in love with the same girl, a French nightclub performer named Fifi. Each man tries to outdo the other to win her heart.
Jean and Marise, young lovers forced from their homes, flee to Paris. Irrevocably separated there, their lives deviate into the slums and hard labor of low-class French society. All the while, the two desperately search for one another.
Francis, a young man, recalls in his memory the horrible experiences he and his fiancée Jane recently went through. Francis and his friend Alan visit The Cabinet of Dr. Caligari, an exhibit where the mysterious doctor shows the somnambulist Cesare, and awakens him for some moments from his death-like sleep.
When a couple of scammers hold young Alice Faulkner against her will to discover the whereabouts of letters whose dissemination could cause a scandal affecting the royal family, Sherlock Holmes decides to take over the case. (Considered lost, a copy was found in 2014, in the vaults of the Cinémathèque Française.)