This is a brief animated piece featuring the titular character in a fight ostensibly from a superhero serial of the mid 1940’s. The episode shown is Chapter 13 The Bosom of Terror. In it, Rex and his plucky assistant Penny must journey to South America to stop the evil genius Eval Schnitzler and his henchwoman Greta Schultz from boring into an active volcano and releasing the hot magma energy. The drill is hidden inside a temple located in the mountains. The interior of the temple is lined with bizarre statues of Indian women. Rex and Penny crash in the jungle and while Penny repairs the plane, Rex investigates.