Earthbound (Space: 1999)

Earthbound is the fourth episode of the first season of the science fiction television series Space: 1999. It originally aired on September 26, 1975.

The episode revolves around the discovery of an alien spacecraft containing the frozen bodies of what appear to be humans in suspended animation. Initially, the Alphans are excited by the prospect of finding other members of the human race, but this hope quickly diminishes as they uncover secrets about the ship and its crew.

The alien vessel, revealed to be from the planet Earth, predates Moonbase Alpha by several centuries. It is discovered the ship was part of a secret mission to find a new habitable planet. The frozen humans are not in suspended animation for travel, but are actually in a state of cryogenic preservation as they were dying of a plague that wiped out nearly all of Earth's population. Their mission was to find a cure, but they failed.

The episode explores themes of hope, despair, the dangers of unchecked scientific ambition, and the ultimate fragility of humanity. It questions the ethics of potentially resurrecting individuals carrying a deadly disease and the consequences of interfering with the past. The Alphans must grapple with the moral implications of their discovery and decide whether to attempt to revive the frozen humans, potentially unleashing a deadly plague upon themselves and the galaxy. In the end, the decision is made not to revive the crew due to the potential risk, leaving Moonbase Alpha alone with the knowledge of Earth's fate.