Lizzie Martin comes to London at the invitation of her godfather's wife to become her companion. On the way to the house where she will live, she sees a cart on which a corpse lies. Lizzie considers such a meeting an ominous omen. Later it turns out that this is the body of the murdered Madeleine Hexem, a former companion, whose place is destined to be taken by Lizzie. Lizzie, a brave and straightforward girl, takes a risk, deciding to independently find out who killed her predecessor. Inspector Ben Ross is leading the investigation from Scotland Yard. He is Lizzie's countryman and remembers her as a girl. At one time, Lizzie's father, Dr. Martin, paid for Ross's schooling, and Ross considers him his benefactor.