A reporter gets himself sent to prison so he can solve a murder behind bars.

Gangster Ed Slayden asks reformed criminal Mike Eagan for help after he kills a man in a robbery. Eagan refuses, and to escape Slayden's threats, he hits a policeman, hoping to be sent to jail for thirty days, enough time for Slayden to find someone else to help him. Because this is Eagan's second offense, however, the judge sentences him to two years in prison. Eagan remains silent when reporter Ken Williams begs him to explain his actions, but Ken finally gets the true story from Jane Rogers, Eagan's secretary. Ken then tips the police, who arrest Slayden. Believing that Eagan was the informant, Slayden manages to be sent to the same prison where Eagan is serving his sentence, planning to get his revenge. Dan Stone, one of Eagan's guards, also holds him responsible for the death of his son years earlier. On visiting day, Jane tells Eagan that his nightclubs are losing money. Eagan consoles her, explaining that he has some money hidden away and plans to retire when he is released. On the day he is to be paroled, however, he is found murdered. Williams investigates the murder, his attention focusing on a book which Eagan repeatedly checked out of the prison library. Before he can find it, the librarian is knocked out and the book is stolen. Suspicion falls on Stone, until he is kidnapped by Slayden, who uses him as a hostage when he escapes from prison. Slayden heads for Jane's apartment, thinking that she knows where Eagan's money is hidden. The police find them together and are about to arrest both of them when Ken reveals that the killer was another guard, Dan Varner. Eagan, grateful to Varner for saving his life, told him about the money, and the money was the motive for the murder. The mystery solved, Ken proposes to Jane, with whom he has fallen in love.