Cash Holliday and Marshall Earp are the illegitimate sons of the most notorious gunslingers in the West. Despite a lingering bad economy in 1896, the two operate a flourishing detective agency, largely thanks to selective partnerships. When Sheriff Kristof Varga hands Marshall a bounty for the infamous Cactus Kid, they realize their business could change overnight. But Cash receives a letter stating some of his late father's possessions are in Tombstone and he becomes interested in a different pursuit. Faced with lying to his best friend, crazy superstitions, a girl with a mysterious past, and a Pinkerton agent who is hot on their trail, Cash must decide if he's willing to risk their lives for the secrets of a father he never knew.