Frankie J. Parker Calvin Lockhart is a Los Angeles radio disc jockey who, in his spare time, takes karate lessons at a school run by his friend Charles Atkins Jim Kelly. A woman in a rental car, newly arrived from Chicago, listens to Frankie’s show and soon meets him at a nightclub owned by Tank Robertson [Rockne Tarkington], a former football player who is part of Frankie’s circle. There, she introduces herself as Melinda, and Frankie invites her to a party on Tank’s yacht, a move that stirs jealousy in his girlfriend Terry Davis Rosalind Cash.
Frankie takes Melinda to his apartment, unaware that they are being followed by a thug. They share a night of passion, and the next morning Melinda tells the womanizing, easy-going Frankie that he has the makings of a more serious, substantial man. After Frankie leaves for work, he begins to realize he has developed genuine feelings for Melinda. When he returns, he finds the apartment ransacked and Melinda murdered.
It turns out Melinda’s real name is Audrey Miller, and she was the former mistress of a Chicago gangster named Mitch Paul Stevens, who is trying to recover a mysterious item Melinda took with her to LA. A junkie named Marcia tries to take Frankie at gunpoint, but he overpowers her; in the struggle, Marcia ends up dead. Frankie learns that Tank Robertson is a business associate of Mitch and owes him money, tying the danger to Frankie’s circle.
The item Melinda took is kept in a safe-deposit box at a bank, and the key to it was mailed to Frankie before Melinda’s death. Unable to access the box himself, Frankie lets his girlfriend Terry impersonate Melinda to retrieve the item, which turns out to be a gold cigarette case. Inside the case is a tape recording that could incriminate Mitch in a crime. Terry is taken prisoner, forcing Frankie to travel to Mitch’s mansion for a tense trade arrangement, bringing Atkins and a group of karate students along for protection.
They discover Terry held in a snake-filled cage, and Frankie, Atkins, and the others rush to her rescue. Frankie then holds Mitch at gunpoint, only to learn that the tape is inaudible—the result of Mitch’s dirty trick. Believing he has escaped accountability, Mitch laughs, but Frankie’s rage erupts as he nearly beats Mitch to death for Melinda’s killing. After the confrontation, Frankie and Terry share a tender moment and walk away together, stepping into the night toward his car.
