The Mafia runs an illegal betting sweepstake in Florida. Johnny Firpo, a US Marine from Miami, is tasked to bust this ring. He is tasked with teaming up with gambler turned trucker Charlie Firpo, who is - unknowingly - Johnny's half-brother. To ensure he gets help from Charlie, whom had given up on gambling in an earlier incident against Paraboulis The Greek which resulted in Charlie smashing everything in sight and allegedly breaking Paraboulis' nose, Johnny tricks Charlie into giving him a ride to Miami, then stealing the truck Charlie rode in using the henchmen of Paraboulis as a distraction after offering said truck as payment for losing a poker game.
Johnny reveals that he's Charlie's brother after another fight against the Mafia during a car rally, and telling Charlie he was wanting to earn money from gambling for an eye operation for their father, whom was supposedly blinded by the Mafia, though unknown to Charlie this is a ruse in order to get him to co-operate. This co-operation is first coming to fruition in a horse race where Johnny takes the place of the rider of the horse Lightning Rod, Sam Stallion, in order to win the race, while Charlie tricks one of the 'bookies' into taking an 11-to-1 odds bet on Lightning Rod. Afterwards, Charlie teaches Johnny about the various hands dealt in poker, though an encounter between their father and Paraboulis' henchmen nearly exposes the ruse, but Johnny distracts Charlie enough to make the ruse still stand for the time being.
After winning another betting match, Johnny is then taken to a cruise ship in international waters, the main base of operations of Paraboulis the Greek, where he is invited to a 'friendly family game' of poker with Paraboulis after making a big win at the roulette table, where he uses Charlie's teachings to win match after match, though Charlie intervenes after the ruse is exposed, initially confronting Johnny about it, before the two brothers turn on and beat up Paraboulis the Greek and his henchmen, rolling up the entire illegal gambling ring.
