The movie opens with a scene of a high-stakes poker game happening in a Miami hotel, where a group of crooked card sharks led by a man named Kirk are rigging the game in their favor. Johnny Firpo, who is stationed on a naval ship in the nearby port, is sent on shore leave to work with the Miami Police to bring down the card sharks.
Johnny soon discovers that the only way to catch these crooks is to infiltrate their inner circle. He seeks the help of a retired gambler named Charlie Firpo, who is known to be one of the best card players in Miami. However, Charlie is reluctant to get involved, as he has left the gambling world behind and is now running a transfer truck business.
Desperate for Charlie's help, Johnny steals Charlie's truck and uses it as leverage to force him to come on board. The two men soon discover that they are half-brothers, with the same father but different mothers. Johnny tells Charlie that their father is in need of an expensive eye operation, and they need to raise $100,000 to cover the costs.
Charlie, who has a heart of gold, agrees to help Johnny raise the money by returning to the gambling scene. He soon proves himself to be a skilled gambler, and the two men work together to win big in a series of high-stakes card games.
However, their success does not go unnoticed, and the group of crooked card sharks led by Kirk begins to close in on them. Johnny and Charlie find themselves in grave danger as they race against time to raise the money they need to save their father's life.
In the end, Johnny and Charlie defeat the card sharks and walk away with the $100,000 they need for their father's operation. They both bid each other farewell, as Johnny returns to his naval duties and Charlie continues to run his transfer truck business - content in the fact that he was able to help his brother when he needed it the most.