Challengers of the Unknown #6

Answering an SOS from a boat that has struck an ice berg, the Challengers soon learn that it was a trick by aliens from outer space and are taken prisoner. They are then forces to be exhibits in the Space Circus. Forces to fight gigantic beasts from other planets, the Challengers eventually break free from their cage and free the other captive species and lead a revolt which leads to the eventual capture of the ring master. Taking the ship back to it's home planet, the Challengers turn the ringmaster over to the authorities there before being returned home.