The Partridges agree to do a concert for a real "captive audience" – the convicts at the Federal Penitentiary. Inmate Hank Bourlord's only reason for arranging the concert is to sell the Partridge family several new love songs. When the show is over, Hank tries to see Shirley but can't get past Reuben Kincaid. To prevent them from leaving, Hank, who's a hospital orderly, uses his convict pal, Monty, as his patient and convinces the Warden that Monty's "illness" may be contagious. Then the warden places the entire prison under quarantine – which means Reuben, Shirley and the kids must spend the night in jail. The prison doctor's office will only sleep four, so Keith, Danny and Reuben are assigned to a regular cell amid the convicts.
The next morning, after receiving a mysterious, threatening note, Shirley learns that Hank has stolen the music from Max, a scar-faced, mean-looking convict who is the leader of all the inmates. Everyone, especially Keith, wants to record the songs, but Max won't sell. Shirley finds out that Max is afraid he'll lose the respect of his "cons" if they know he wrote poetic love songs. By promising to publish the music under a pen name, Shirley finally gets Max to change his mind and sign a contract.