A small time pickpocket runs afoul of what looks like a sweet old lady in old fashioned clothes with a comically old automobile, but is in fact a ruthless head of a crime ring. He's shot and put into a coma. Blackie senses the lady, a known ex-con, is up to something as she and her mob plan an art museum heist.
Barney Stevens, an East Coast bank robber, escapes from prison and skips to LA with his partner, Dave Brubaker. However, he is recognized by a bank teller before committing a new robbery. Stevens is arrested, and Brubaker seeks revenge - by killing the teller. The teller's wife sees the shooting, and Brubaker determines to get her too. Luckily, she is a friend of Boston Blackie.
Blackie sees a robber jump into a taxi. After a car chase the robber gets away, leaving the taxi driver with a bullet in his arm. The taxi driver is an ex-convict, who Blackie once sent to jail. Blackie believes the taxi driver now to be an honest man and doesn't think he is mixed up in the robbery.
Nick Vincent, an out-of-work youth, takes advantage of a grocery store owner who thinks he's an armed robber when the young man demands prompt service with one hand jammed in his jacket pocket. Seeing how easy it was to steal nearly two-hundred dollars accidentally, Nick purchases a gun and plans to enter a life of crime. At Nick's father's request, Boston Blackie attempts to reason with Nick he can begin his one man crime wave.