While on a run, Hickok meets Noah Dixon, a free black man being harassed for helping slaves. Hickok and Noah arrive in Sweetwater with Noah's old friend, who is helping to organize an underground railroad. Meanwhile, the other riders try out new cooks.
A legend grows as a ruthless bank robber poses as Wild Bill Hickok, and the real Hickok must find and expose the phony or suffer for someone else's crimes. Meanwhile, Cody's attempted prank on Buck backfires.
Fearing a cholera epidemic as people continue to fall ill, a mob becomes determined to eliminate every suspected carrier, including a mentally challenged young man who arrived in Sweetwater from a town plagued with sickness.
The pretty new school marm catches Kid's eye and he finds himself drawn into her problems when an old beau comes callin'. Lou and Jimmy bond on a special run but their fun is derailed when someone looking for revenge takes Lou hostage.
Ike meets up with one of the men that was there when the rest of his family was killed and has to decide if turning him in is worth it since he's changed his life. Meanwhile the other riders are on the trail of a mysterious monster.