U. S. astronauts Mike Blaiswick, Nick Grant, and Duncan blast off from Cape Kennedy on the first American space flight to Mars. As they approach their rendezvous with an orbiting supply ship, they are horrified to see the frozen, lifeless bodies of two Russian astronauts, the victims of an unsuccessful Soviet flight to Mars. Upon landing on the planet, the astronauts find the body of another Russian. While Grant takes the body back to the spaceship, Mike and Duncan are attacked by a strange mechanical object called a polarite, which is activated by the sun's rays. After immobilizing the polarite, they contact Earth and are ordered to terminate their mission immediately. Before they can do so, however, a huge glowing sphere neutralizes the ship's rocket power and engulfs Duncan. Mike and Grant notice that the Russian astronaut has returned to life, and he tells the Americans that the polarite can only be stopped by blocking its source of solar energy. Though it costs him his life, Grant uses his laser gun to temporarily reduce the magnetic hold of the planet, thereby enabling Mike and the Russian to return safely to Earth.