Nearly a year after the children landed on a new world, Judy struggles to lead them in repairing the Jupiter's engine in order to escape the planet. Elsewhere, the survivors of the Resolute try to stay hidden from the enemy.

Judy discovers her father, Commander Grant Kelly, in stasis on the surface, while Penny and Will explore a dark cave with a possible connection to the robots. Maureen and John bring Don on a mission to recover the parts of a destroyed robot.

When Will goes to document an ancient alien city he makes a disturbing discovery beneath the surface of the planet. John and Maureen are forced to trust Scarecrow in hopes of securing an alien engine, and Commander Kelly takes matters into his own hands.

After S.A.R. baits the Jupiter 2 the kids resolve to return and try to rescue their parents, knowing they are being drawn into a trap.

The Jupiter 2 crash-lands on a hostile planet, leaving the Robinsons separated and Maureen reliving memories of her past choices ... while the enemy hunts for the survivors.

The family regroups only to discover a new threat to the human colony on Alpha Centauri – and Will puts himself on the line to try and put an end to S.A.R.'s murderous pursuit.

The Robinsons finally arrive on Alpha Centauri amidst a crisis, bringing a warning that the alien robots could attack the colony at any moment ... but are surprised when no attack arrives.

The Alpha Centauri colonists brace for the robots' attack. But after Penny makes a surprising discovery, Will puts everything on the line in a last-ditch effort to end the war with the robots.