A group of people from different backgrounds have one thing in common: when they hear the world "gumball" whispered by one of the others, they know that it's time for the Gumball Rally: a no-holds barred, secret, winner-take-all rally across the USA.

With his bronco-busting career on its last legs, Junior Bonner heads to his hometown to try his luck in the annual rodeo. But his fond childhood memories are shattered when he finds his family torn apart by his greedy brother and hard-drinking father.