Somehow, unaccountably, the Asteroid Medusa had broken orbit and was now plummeting irresistibly toward Earth! A collision, if one occurred, would mean the end of this planet. Drastic action was called for and a drastic plan executed: a spaceship blasted off from Earth to intercept the Asteroid Medusa. Its mission: to detonate an anti-proton bomb upon the run-away body and blast it into oblivion.