Bill O'Brien is promoted to lieutenant in the police department for his arrest of Mike Patello, gang leader and racketeer, for murder.  Ruth Dale, who loves Bill, is concerned when her brother, Johnny, who witnessed the murder, proposes to testify against the racketeer.

Meanwhile, Captain Antrim informs Bill that his father (John O'Brien) has just been released from prison and does not know his son is a policeman.  On the way from prison, John O'Brien meets Limo, a former cockney pal who recognizes Bill and keeps John from seeing his son.  Later, John arrives intoxicated and is enraged, forcing Bill to knock him unconscious.  John is arrested for robbery but returns the loot to save his son from disgrace.

Johnny Dale is killed before testifying against Patello, who is released but then confronted by John, who proves his guilt.  When Patello struggles with the police, he is killed.

Bill plans to resign, but confident of Ruth's love, he decides to remain on the force.