Captain John Strong leads a group of space-pioneers to Ganymede. Along with him are included Peter and his sister Peggy. Peggy is in love with Captain Strong. Settling on Ganymede becomes complex when a man named Maddock discovers diamonds, gold, and uranium. Maddock and his cohorts desire to return to Earth with their new riches. Captain Strong assures Maddock the Ganymede settlement is the true treasure. Maddock and John square off with fists, with Maddock as the decided loser in the argument.