Hotshot street-racer Phil Sandifer (Contino) is working as a truck driver when he is harassed by a sports car on the highway. He meets the driver, Jana (Giles), at a club. Jana challenges Phil to a race; she runs Phil off the road, and he loses. At the same time, Phil's best friend Sonny is run off the road and killed by an unidentified assailant (VeSota).
Phil is arrested for destruction of city property, trespassing, reckless driving, and hit-and-run and manslaughter for Sonny's death. The hit-and-run and manslaughter charges are dropped, but Phil is found guilty of the other charges, placed on probation, and stripped of his driver's license. Phil then investigates Sonny's murder. He initially suspects Jana but quickly realizes she is not to blame, and she joins his investigation.
The investigation leads to nightclub owner Sidney Chillas (Sonny's assailant) and his near-sighted lackey, Bruce. Chillas hires Phil as a singer under the alias "Daddy-O," which serves as a cover for Phil to transport illicit packages using a phony driver's license. After being beaten by drug dealers who mistake him for "Pete Plum"—the name on his phony license—Phil realizes the name was previously used by Sonny. He concludes that Sonny had worked for Chillas, stolen drug money, and was killed as a result.
Phil and Jana witness Chillas having a falling out with his business partners and are caught; Jana is taken hostage. Chillas orders Phil to retrieve a stash of money in exchange for Jana's release, sending Bruce along at gunpoint. Bruce attempts to steal the money, but Phil disarms him and flees. Phil confronts Chillas in a liquor cellar and knocks him out. Bruce returns and takes Jana hostage again, but the police arrive and arrest both Bruce and Chillas. The movie ends as Phil is asked to sing.
Dick Contino as Phil Sandifer
Sandra Giles as Jana
Bruno VeSota as Sidney Chillas
The film was released by American International Pictures on a double bill with Roadracers.
It was featured in episode #307 of Mystery Science Theater 3000, paired with the short Alphabet Antics. The episode features a parody of the film's song "Rock Candy Baby," performed by Joel Robinson, Crow T. Robot, and Tom Servo as "Hike Your Pants Up." This episode was included in the Mystery Science Theater 3000 Volume XXXIII DVD box set released by Shout Factory in July 2015.
In the 1994 film Pulp Fiction, a poster for Daddy-O is visible in the "Jack Rabbit Slim's" restaurant. The 1994 James Ellroy short story collection Hollywood Nocturnes includes "Dick Contino's Blues," a fictionalized take on the making of Daddy-O and its backstory.