Bruce Kerrigan, a member of the traffic police, is selected to act as a graft-collecting tool for Mat McGuire, a politician. While directing traffic at his corner one morning, Kerrigan becomes acquainted with the mayor's daughter, Ethel Drew, when her auto collides with another machine. Ethel requests her father to have "Officer 405" assigned for special duty as doorman at the Mayor's reception that night. While on duty at the reception, Kerrigan captures Whitey, the dope, who enters the mayor's study to steal evidence which the mayor has secured regarding the operation of gambling houses and other vice centers. Later Kerrigan is caught in the act of collecting graft, and when he will not divulge the name of the man higher up, he is discharged from the police force. Assuming the disguise of a crippled tramp, he gets employment as a janitor in McGuire's political club, where he is able to steal the evidence secured by Whitey from the mayor's home.