While Judy sets out to find Grant Kelly, Penny and Will explore a mysterious tunnel. Light years away, Maureen, John and Don hunt for SAR's remains.

Scarecrow helps Maureen and John plot an engine heist. Judy returns to camp with new passengers. Will makes a startling discovery in the alien city.

As the adults race to destroy all clues to the location of Alpha Centauri, the Robinson kids receive an ominous message from SAR.

The Robinsons race to get help for Will, warn the other colonists and activate a secret defense system. Vijay tags along with Penny on a risky outing.

As the battle for Alpha Centauri unfolds, the Robinsons and their friends risk everything to restore peace and pave the way for a better future.