June calls in the Challs when objects vanish from a rooftop restaurant. They find that aliens are trapping people in cylinders below a mysterious cloud. While Ace and Red discover a flying platform within the cloud controlled by alien criminals, Rocky and Prof battle a giant metal insect. Two aliens destroy the insect and explain that they’re scientists who commanded the platform until criminals seized it. With the aliens' help Rocky and Prof go to the platform, reunite with Ace and Red, and brawl with the criminals. The good aliens trap everyone, then release the Challs before heading home.; Burt Langdon has stolen the Horn of Herix from a museum. The Challengers track Langdon to a valley where a Doom Box, a legendary weapon, is hidden. Weird boobytraps slow the Challs: an alligator, a tree-turned-elevator, and giant robot Romans. They find the horn discarded, then the Doom Box guarded by a flames and a two-headed dragon! Ace blows the horn and a ray from the box drives back the dragon and flames. Langdon’s gang attacks, grabs the box, and runs. Ace blows the horn again, and the box explodes, because the horn was made to destroy the box if it were moved from its ring of flames.