An innocent young woman arrives in London looking for work and walks into an ambush, in which gangsters knife an accomplice who has cheated them. The wounded man staggers with her to a cheap hotel, where he dies after begging her to tell his brother at The Green Cockatoo club. Going there, she is followed by police and hides in an upstairs room. It is that of Jim, the brother, but he does not identify himself to the stranger. When the police leave he escorts her out, but is followed by the gangsters. In another knife fight he gets away and takes her to a safe house. The police turn up, this time to take him to the morgue to identify his brother. When they leave, the gangsters abduct the girl. Looking for the gangsters, Jim turns up and in another fight immobilises them. The police arrive to arrest the gangsters, while Jim and the girl head for the country.
