Chester "Ace" Bernstein gets released from prison after serving three years and is determined to get back to the tracks. He has his friend Gus buy the horse because of his probation. Meanwhile, Jerry and Marcus team up with Renzo and Lonnie and win the biggest score of $2.6 Million from the Pick 6 and are biding their time to step forward. Leon, a aspiring champion pushes a horse that pays off big. At the same time, Walton is wanting to get back in the game despite his age, but needs a good horse and rider. That might be in the eyes of an Exercise Girl.
Ace meets with his parole officer and starts to line up potential investors as a public face for his next big venture. Meanwhile, Renzo stumbles into a risky proposition by making claim on a horse trained by Escalante; Jerry takes a beating at a high-stakes poker table; and Walter finds a seasoned jockey for his prized thoroughbred, much to Rosie's dismay.
Jerry pursues a deal to buy the horse that Renzo lost to Mulligan while also talking to Escalante about training it. Meanwhile, Walter mulls a change in jockeys after Gettin' Up Morning's first race ends badly; and Ace gives a young whiz kid the opportunity of a lifetime.
Ace meets with Claire about a charitable endeavor for prisoners, and discusses his new venture with an old partner. Meanwhile, Jerry's gambling nemesis lures him into a dangerous game that may require an intervention by his racetrack buddies; and Walter turns to Rosie to be his new jockey.
Ace takes the reins when Escalante surprises Gus with his decision to race Pint of Plain with an inexperienced jockey in the horse's debut. Meanwhile, Marcus delves into the meaning of his friendship with Jerry; and Claire accompanies Ace to the track after accepting his very generous donation.
Ace meets with a track owner and his parole officer, but sends Nathan Israel to discuss business with his fellow investors, who scheme to stay one step ahead of their new partner. Meanwhile, an earthquake has a curious effect on Joey's state of mind; and Leon and Rosie find their racing skills questioned by higher authorities.
Ace has a relaxing visit to the prison-outreach retirement farm for horses, but Nathan Israel has a rougher time trying to persuade Ace's new partners of his boss' sincerity. Meanwhile, Walter discusses Gettin' Up Morning's ownership with a lawyer and decides on his next rider; Jerry teams up with a card dealer to play their way into a poker tournament; Lonnie makes a solo claim on another horse; and Rosie asks Joey for representation.
Ace reacts decisively to a new wrinkle in the racetrack deal, but it's probably not a move that Smythe will take lying down. Meanwhile, Walter tries to concentrate on the historic Western Derby, in which his horse will go head-to-head with Gus'; Rosie's good news isn't so great for Leon; and Jo is injured in a stable accident.
In the series finale, Gus draws on past experience to deal with a present threat, and Ace is floored by a surprise visitor. Meanwhile, Walter's Gettin' Up Morning and Gus' Pint of Plain wow the crowd in the Western Derby; Mon Gateau's owners prepare for their biggest race so far; and Escalante checks in for frequent updates on Jo's condition.