Friends and, years later, in-laws, Carlos Rivera and Manny Gonzalez, grow up in a tough South Bronx neighborhood and spend a good part of their youth fighting rival neighborhood kids.

With a stroke of luck, the boys learn how to box at the Police Athletic League around the same time Manny starts dating Carlos' sister, Maria. She doesn't care for this "boxing thing" but figures it's better than them getting in trouble on the streets. Fast learners, Carlos and Manny, become undefeated fighters and rise to the top of their weight class.

Promoters and boxing fans worldwide clamor for the in-laws to fight, with the winner getting a shot to fight for James "The Assassin" Lewis's title. Fans pack Madison Square Garden to the rafters as the excitement reaches near pandemonium. Both fighters put their friendship aside and agree to fight with everything they have. The bout lives up to the newspaper hype as the friends, now adversaries, go the distance—ten rounds with neither warrior conceding. As the last bell sounds, Carlos collapses in his corner.

Everyone in the ring frantically tries to save Carlos. The crowd falls silent.

Nine days later, Carlos is gone. But where he ends up changes everything.