Irish ventriloquist Jonathan West visits a pawn store and cashes in the last of his goods for money. The one thing he refuses to sell is his dummy, Little Caesar. Back at his apartment, he makes dinner and talks to Caesar, assuring him they'll soon have booking like Caesar's last owner. Caesar talks back to a startled Jonathan, telling him that he's finished.
As Jonathan prepares for his show, his next-door neighbor girl Susan comes in and wants to hear Caesar talk. He finally gives in and Susan mockingly says he won't get the job. Once she's gone, Caesar tells Jonathan to keep Susan out of the room.
At the club, Jonathan gives a performance for the manager, Mr. Miller. Miller is less than impressed and Jonathan goes home. His landlady, Mrs. Cudahy, wants the rent and when he can't pay, gives him the card of her cousin at an employment agency. As he leaves, Caesar watches from the apartment. At the agency, Jonathan is forced to explain that he's not a citizen yet and has never held a job outside of show business. The agency man, Mr. Smiles, tells him he'll call.
When Jonathan comes back, Susan taunts him some more. Jonathan goes to his apartment and admits he needs some money so he can think clearly. Caesar calls him a clod and says he's had enough. From now on he's going to tell Jonathan what to do. That night, Jonathan robs a neighborhood delicatessen while carrying Caesar along. The next morning, he pays Mrs. Cudahy and goes back to his apartment to wonder what's happening to him. Caesar tells Jonathan he's penny ante and from now on he's going to lose his accent and hit the streets. They're unaware that Susan is on the other side of the door listening in.
Later, Susan sneaks into Jonathan's room and tells Caesar to talk to her. The dummy doesn't respond to her. As Jonathan comes in, he sees Susan coming out and demands to know what she's doing. Susan walks off and Jonathan goes to Caesar. The dummy assures him that he only needs to do one more job and he'll be set.
That night, Jonathan and Caesar break into Miller's office at the theater and Jonathan opens the safe. He gets the money and leaves, but the watchman catches him on stage. Jonathan claims that he's there to meet Miller and has Caesar say a few words. The watchman buys Jonathan's story and tells him that Miller left earlier.
Back at his apartment, Jonathan discusses the situation with Caesar as Susan listens in. The next morning, Susan is eating breakfast when her aunt Mrs. Cudahy reads a newspaper article about the robbery. Susan calls the police and they arrive to ask him where he was. Jonathan claims he didn't go out but the police have talked to the night watchman and can confirm he was there. Jonathan tries to get Caesar to provide him with an alibi. Caesar has nothing to say and Jonathan falls apart. The police take him away and Susan hears Caesar whisper to her. The dummy calls her over and tells her that he knows she ratted out Jonathan. Now Caesar wants to get out and have her take him. All she has to do is get the money Jonathan hid and dispose of her aunt.