Returning to
New York City from Europe, Boston Blackie tries unsuccessfully to strike up a conversation with attractive fellow
ocean liner passenger Marilyn Howard. He later rescues her when she is accosted by a man. However, when he tries to follow her, he runs into his friendly nemesis, police Inspector Faraday, who wants to take him in on suspicion of stealing some pearls. Knowing that Blackie's word is good (and that handcuffs are useless against him), Faraday merely confiscates his landing card. However, when Blackie discovers the body of the man who had bothered Marilyn Howard deposited in his suite, he has to break his word and debark to clear his name. He trails Howard to the
Coney Island amusement park. She has been followed by two men and is struck by a poisoned dart. Before dying, she tells him enough to send him to the Mechanical Man, a
midway performer whose act is pretending to be a robot or
automaton. Soon after, the two killers show up to report to their boss, the Mechanical Man, forcing Blackie to flee once again. He hijacks the car belonging to Cecilia Bradley and manages to lose his pursuers after a high-speed chase. Cecilia decides to help Blackie, despite his attempts to keep her out of his troubles. They learn from a radio news broadcast that Howard was a spy. Blackie eventually discovers that an espionage ring led by the Mechanical Man is trying to take a stolen navy bombsight out of the country. Faraday and his men follow Blackie to the midway to arrest him and prove handy in apprehending the spies. As a reward, Faraday decides to forget about the evidence linking Blackie to the theft of the pearls. ==Cast==