Chester Morris is back as Boston Blackie along with George E. Stone as his pal The Runt. Also returning is Richard Lane as Inspector Farraday. Farraday deputizes Blackie to help recover a stolen diamond.
A fundraiser is being held at the Carleton Plaza Hotel. Various jewels are on display including the half million dollar Blue Star of the Nile. With the help of hotel employee George Daley two small time crooks cause a distraction and Daley steals it for them.
Inspector Farraday tells the press Boston Blackie is the thief. It’s really his way of getting Blackie to come see him. He gives him a badge and tells Blackie he can use his own methods to recover the diamond. Blackie disguises himself as an old man and Runt is a cab driver. Blackie searches the display room and Daley’s office and figures out how the theft was accomplished.
An alert reporter. Dorothy Anderson, sees through his disguise and calls the cops. Blackie is arrested. He tells Farraday he’s escaping and that makes headlines and Farraday looks like a chump to the commissioner.
Daley lives with his sister Eileen. She’s a switchboard operator at the hotel. Daley hides the diamond in her purse inside a dresser drawer. Eileen is going out and switches purses. He tries to chase her but is stopped when the bad guys show up. Daley tells them what happened. They warn him to get it back that night.
Blackie was there earlier. Eileen follows him to a restaurant. He tells her how her brother stole the diamond. Runt comes in a warns Blackie that Dorothy is outside and he takes off. Dorothy comes in and goes out the powder room where she switches purses with Eileen. (How she knew to get the exact same purse is anybody’s guess).
Later out on the street Daley hands the stone over to Blackie. The bad guys show up. One of them kills Daley. They take off with Blackie and The Runt. Farraday puts out an alert for Blackie as a murderer. From here on out it’s all comedy.
Don’t take any of this seriously and you’ll be entertained.