A man who fights his way to success learns the people who helped him may be his biggest enemies in this action drama. B.J. Hammer (Fred Williamson) is a dock worker who used to box in the Golden Gloves and still knows how to handle himself in a fight; when he gets into a brawl at work, he's seen in action by an associate of Davis (Bernie Hamilton), a flashy businessman who manages boxers. Davis thinks Hammer has potential, and offers him a contract. Soon Hammer is training with Professor (Mel Stewart, an experienced boxing coach, and begins romancing Lois (Vonetta McGee), one of Davis's secretaries. After easily winning several fights, Hammer's career is on the rise and he seems poised to become a championship contender. But Davis isn't just interested in boxing; he's an underworld kingpin who also traffics in drugs and prostitutes, and often uses washed-up fighters as pawns in his criminal games. Hammer soon learns just how Davis operates when his manager orders him to take a dive in an upcoming fight, and when Hammer refuses, both he and Lois could face deadly retribution. Also starring William Smith and D'Urville Martin, Hammer was a major box-office success that established Fred Williamson as one of the major stars of the 1970s blaxploitation boom; the film also included an original score from soul music legend Solomon Burke.