Stodge City is in the grip of the Rumpo Kid and his gang. Mistaken identity again takes a hand as a "sanitary engineer" (plumber) by the name of Marshal P. Knutt is mistaken for a law marshal! Being the conscientious sort, Marshal tries to help the town get rid of Rumpo, and a showdown is inevitable. Marshal has two aids - revenge-seeking Annie Oakley and his sanitary expertise