In the Christmas spirit, Boston Blackie, Chester Morris arranges a festive variety show for the inmates at his old school, hoping to lift their spirits with entertainment led by the boisterous clown Roggi McKay, George McKay. The act features Eve Sanders, a showgirl who has already visited her prisoner brother, Joe Trilby, the maximum number of times allowed that month, yet Blackie, in a rare display of kindness, invites her to stay with the troupe. The staging is crowded with chances for mischief and heart, and the mood is as bright as the holiday lights, even as the shadow of prison life looms over the performers.
On the bus to the venue, Inspector Farraday, Richard Lane, and Detective Mathews, Walter Sande, ride along to keep an eye on Blackie. The tension thickens when Joe Trilby unexpectedly makes a getaway from the prison, using Roggi’s costume and makeup to slip free, leaving Farraday convinced that Blackie played a role in the escape. The chase tightens as Blackie heads to Eve’s apartment, hoping to calm the situation, while Eve herself arrives with a mix of worry and resolve.
Joe arrives at Eve’s place insisting he’s innocent, claiming he was coerced by Duke Banton and a man named Steve into driving to the crime scene without knowing why. He explains that when the robbery was foiled, his supposed conspirators fled, leaving him to face the music. Joe’s desperation turns sharp: he declares that he intends to kill the pair regardless of the consequences. He seizes Blackie’s disguise and binds him, but Eve soon arrives and frees the captive mastermind, setting the stage for a tense cat-and-mouse across the city’s holiday backdrop.
Following this, Blackie and his loyal sidekick, the Runt George E. Stone, press on toward Duke Banton’s place, only to find a dead body where their target should be. Joe barges in again, maintaining he did not commit the kill. As the police close in on the building, Blackie engineers a swap: Joe trades places with Banton after Farraday has already examined the corpse. The supposed corpse is hauled away in an ambulance, and Blackie is taken into custody, but he manages to overpower Detective Mathews and slip away by donning the detective’s uniform.
From a tip supplied by Jumbo Madigan, a shrewd informant, Blackie pieces together the remaining clue: the other robber is taxi driver Steve Caveroni. Eve is enlisted to pose as a fare to lure Caveroni to Banton’s hotel room, turning the trap into Blackie’s advantage. Caveroni, feeling in control with a gun at hand, is coaxed into a confession: he admits killing his partner and that Joe Trilby is innocent. The discovery is almost thwarted when Farraday and his men listen in outside the door, but the truth comes out just in time. When cornered, Caveroni makes a last attempt to flee but is shot dead, leaving the case closed and Blackie’s name shielded by the evidence he orchestrated.
