Doc is using the jail to quarantine people as they fall ill. The common thread between them seems to be that they all had a dinner meeting together, about the upcoming German festival, at Bendino's restaurant. Doc, at first, suspects some type of food poisoning as the culprit, but then discovers it's really Typhus. Leading citizen Mr. Matthews takes a few of his men over to Bendino's and beat him to death. Matt arrests Matthews and throws him in jail, much to Matthew's disdain with all the patients. When Mrs. Saur, a German resident living outside of Dodge, comes down with the disease Doc has to look elsewhere for the cause. He sets up an experiment that could cause him to come down with the disease himself, and possibly die! (thetvdb.com)