The Wild Wild West (1965)

S3E22 The Night of the Amnesiac

A stagecoach transporting the entire supply of smallpox vaccine for the western states is ambushed and the medicine is stolen. Furman Crotty, a prisoner at Leavenworth, is now insisting on his release along with a full pardon, threatening to hold the vaccine ransom. Meanwhile, Jim West, who was injured during the stagecoach attack, grapples with amnesia. Artemus must race against time to locate both his friend and the stolen vaccine before a devastating epidemic breaks out.