Dick Tracy has been guarding the Black Pearl of Osiris, a relic, which belongs to a religious Egyptian cult. Tracy has kept the pearl in the secret compartment of a ring, given to him by a high priest of the cult. Whilst the police are searching for the Mogul, the head of a society of art thieves who want the pearl, the Mogul visited Pat Patton and hypnotized him. Pat, under the Mogul's spell, succeeded in getting the ring from Dick, but the great detective knew that something was wrong, and followed Pat - confronting the mogul as Pat was handing him the ring...