Strange Gamble

Hoppy and his pals arrive in a remote town to investigate the counterfeiting of both U.S. and Mexican money; his only clues are the name "Mordigan" and a drawing of a comet. He quickly finds out that Mordigan is the town "boss"; but what or who is "the comet", and why are Mordigan and his henchmen intent on persecuting a young woman, her drunken brother, and her deathly ill sister-in-law who've also just arrived in town?