Adapted from Joseph Conrad‘s 1907 novel The Secret Agent, Sabotage (alternately titled, The Woman Alone) focuses on the investigation into a series of terrorist attacks in London. A young woman, Mrs. Verloc (Sylvia Sidney), runs a movie theater with her husband, Karl Verloc (Oskar Homolka), and her younger brother Stevie (Desmond Tester). Soon after the attacks begin, a charming grocer befriends Mrs. Verloc. This grocer is undercover Detective Sergeant Ted Spencer (John Loder) of the Scotland Yard. As he slyly attempts to pry information from the innocent and oblivious woman, she starts to suspect that something is awry with her husband.