During a flight to Mars in the spaceship Mars Gravity Probe 1, Commander Christopher 'Kit' Draper and Colonel Dan McReady are forced to deviate from an asteroid, and they leave their spacecraft in pods. Draper lands on the surface of the Red Planet and survives. He learns how to produce oxygen, and, while exploring the planet, he finds McReady dead in his crashed pod. He also finds the monkey Mona and brings the animal to the cave where he is sheltered. He learns that he can breathe the Martian air for short periods but also needs oxygen. But Mona finds water and an edible plant underground. After a long period alone, Draper feels the loneliness. One day, he sees a spacecraft landing on Mars, and he believes it might be the rescue team to save him. But he finds aliens working on the planet, and some of them are slaves. One of them flees and stumbles onto Draper, and he names him Friday. Now, he needs to find a way to be rescued and return to Earth.