The Challengers stumble upon an alien plot to dismantle the Earth. A mole-creature will slice the Earth apart. A sea monster will hold back the seas. A flying creature will trap the air, and pie-shaped slices of Earth will be stolen by a robotic ship! Ace jets to the ship and finds it's on auto-pilot, run by robots for a long-dead race. The Challengers attack the creatures without success, until they inflate huge balloons that simulate the creatures dying. The robots abort the mission as a failure and depart.; When a villain named Dekkar uses a machine to steal the Challengers' memories, June Robbins must show her amnesiac friends how to defeat their foe. Goading them, she makes them recall their mountain climbing, diving, and other skills. Feigning amnesia, the Challengers get into the villains' castle to fight. June inserts the memory disk into the machine, hits reverse, and restores the guys' memories.; Shorty creates "atomic gunpowder."