Diane Parrish is eager to sell her Augustus Caesar statue to help her sick brother. Joe Buchanan, one of the art dealers handling the auction, warns her to stay away, claiming that an emotional attachment to the work might trigger a scene. She shows up anyway and discovers the statue is a fake. When Joe Buchanan pulls out a gun to silence her, Boston Blackie spots him and fires his own pistol. Parrish is grazed, but Buchanan accidentally kills his partner and the replica's sculptor, Eric Allison.
When Inspector Farraday arrives, he automatically assumes that Blackie is guilty and takes him into custody. Buchanan hides in the hollow fake statue. Then, when the coast is clear, he puts Allison's body (and the incriminating bullet) inside and makes his escape. The replica is purchased by Blackie's wealthy friend, Arthur Manleder. Despite lacking a corpse, Farraday keeps Blackie in jail, but not for long. Blackie switches places with an ice cream man and escapes.
He goes to see Diane in the hospital to obtain information. To get in undetected, he once again appropriates the unlucky ice cream man's uniform and pretends to be Diane's doctor. When he learns why she needs the money so badly, he arranges for his assistant, the The Runt to masquerade as an insurance adjuster to give her $6000 he borrowed from Manleder. The money had initially been intended to pay off a blackmailing Mona, who claims she is Blackie's wife. When Mona shows up and demands the money, Diane realizes that Blackie is her benefactor.
Buchanan arranges to buy the statue from an unsuspecting Manleder. Blackie learns about it, and sees a way to unravel the mystery. He follows the movers back to their lair. Sneaking inside, he overpowers Caulder, one of Buchanan's henchmen. However, Buchanan returns, with Diane as his prisoner, resulting in a Mexican standoff. Meanwhile, both Manleder and the Runt are picked up by the police. Farraday has them released, hoping they will lead him to their friend. The Runt is too experienced to be taken in, but Manleder does return to the crooks' secret underground workshop, where they copy artworks. In the ensuing gunfight, Buchanan is killed, but the shots destroy the electrical circuits controlling the only way in, trapping them all in the soundproof chamber. Blackie comes up with the idea to start a fire in the ventilation shaft, and firemen arrive to let them out.
