In the year 1987, NASA launched space probe Ranger III, with astronaut William "Buck" Rogers, on a 5-month trip around the solar system. However, the craft runs into a meteor storm, which disrupts its life support system and sends it into a long elliptical orbit of the Earth. In the year 2491, Ranger III again approaches the Earth, and is intercepted by the alien flagship Draconia, which is on a peace mission to Earth. Aboard the Draconia, Buck is revived by Princess Ardala and her second-in- command, Kane, whose true plan is to attack and conquer Earth. Buck is sent to Earth with a hidden homing device, which is soon discovered by Earth's Defense Directorate. After Buck convinces the humans of his true identity -- a man from the past -- he helps them to repel the Draconians' attack, with the aid of the mechanoids Dr. Theopolis and Twiki.