 A teen-age rat pack of the Detroit slums, the Purple Gang, headed by psychotic William Joseph "Honeyboy" Willard (Robert Blake), teams with adult hijackers during prohibition and in three years controls the city s underworld. Detective Bill Harley (Barry Sullivan) is given a special assignment to break the gang. To intimidate Harley, Honeyboy and his chief henchman, Hank Smith (Marc  Butch  Cavell), terrorize his pregnant wife, Gladys (Eliane Edwards), who loses her baby and dies. The gang moves in on the cleaning and dyeing industry, which calls in the Mafia for protection. Hank tries to tip off Harley as to where the Mafia hoods are holed up but Honeyboy, mistaking his intentions, has Killer Burke (Paul Dubov) seal him alive in a coffin and drop him in the Detroit river. Honeyboy locates the Mafia headquarters in an apartment building and goes there with two of his men. They break in and machine-gun the three Mafia leaders, Licovetti (Mauritz Hugo), Ricco (Norman Nazaar) and Castiglione (John Indrisano).