In the year 1997, planet Earth is facing an overpopulation crisis and the United States has formed space colonization plans in order to resolve the problem. As a test-run for the project, the futuristic saucer-shaped spacecraft "Jupiter 2" is supposed to transport a single family to to an Earth-like planet orbiting the star Alpha Centauri. The family and an additional crew member are supposed to be cryogenically frozen for the duration of the voyage. The physician Dr. Zachary Smith is secretly an enemy agent who has been tasked with sabotaging the spaceship. Due to his own mistakes, Smith is trapped aboard the spaceship as it launches and the ship is flying off-course, heading towards unexplored areas of outer space. Smith prematurely revives the crew from suspended animation and serves as a reluctant teammate as they attempt to find a habitable planet. The commander of the expedition is Dr. John Robinson, an astrophysicist and planetary geologist. His wife and fellow scientist Dr. Maureen Robinson is a biochemist and her private garden provides the crew with part of its food supply. Their oldest daughter is in her early twenties and she is primarily interested in dating the ship's pilot Don West. The middle daughter Penny has a particular affection for animals, and she soon acquires the chimpanzee-like alien pet Debbie. The runt of the litter is Will Robinson, a nerdy boy whose primary interests are electronics and computer technology.