While Dr. Smith lies sick in bed, the Jupiter 2 arrives at the star system of Alpha Centauri. There are two planets in the system, both of which seem to support human life. The Robinsons are greeted by a friendly young man named Bartholomew who urges them to land, which they do.
Once down on the planet, John is a bit confused by how young Bartholomew and the other officials seem to be. Bartholomew suggests that Will and Penny be taken so they can be “processed,” as is apparently the norm when children arrive. After only slight hesitation, John and Maureen allow it.
Will and Penny are each placed in a small testing booth where a computer asks them a series of questions, all the while playing very loud dance music. The children find this very disorienting, but try to their best.
Meanwhile, the grown-up members of the crew are beginning to feel suspicious. John gets very angry when he discovers that he isn’t allowed to see or speak to his children. He goes off to investigate the matter and ends up getting temporarily knocked unconscious.
After Will finally fails his exams, he is greeted by a teenaged boy called Edgar. Edgar tries to convince him that he no longer needs the rest of his family, but that statement only upsets Will. Penny, however, is beginning to fit in very quickly. She spends her time dancing to groovy music along with all the other hip teens. When John finds Penny, she refuses to go anywhere with him, apparently having been brainwashed.
John informs the other adults of the strange situation. Smith isn’t as worried about the children as he is about being thought of as old and useless, so he wanders off on his own, hoping to find Bartholomew. As he does so, John, Maureen, Don and Judy are put into suspended animation so their memories can be altered.
Much to his horror, Dr. Smith discovers that Bartholomew, Edgar, and all the other local teens are actually aliens. The aliens in turn discovers Smith spying on them and threaten to kill him if he tells anyone else of their true identity. Smith agrees to keep his mouth shut, and Bartholomew transforms him into a teenager.
Smith tries to persuade Will into getting into the spirit of the planet, but Will finds the endless dancing and music to be irritating and runs away. He and Penny find their parents, but are shocked to discover that none of the grown-up members of the crew remembers them. Despite the children’s pleas, the adults get onto the Jupiter 2 and blast off, leaving them behind.
Once the ship is in outer space, the Robot helps John and the others remember Penny and Will. He also informs them that the planet was not Alpha Centauri at all, and that the local teens are all hostile aliens. John turns the ship around and heads back to rescue the children, but Bartholomew refuses to allow the Jupiter 2 to land. He tells Will and Penny that he intends to destroy the spaceship entirely if they won’t co-operate and agree to stay on the planet. It would seem that the aliens teens are stuck in a perpetual state of youth, and are desperate to have the experience of growing up. The believe that a blood transfusion from Penny and Will can help them, and they are willing to do whatever it takes to get it.
Afraid for their family’s safety, Will and Penny try to warn the Jupiter 2 away from the planet. John refuses to back down, and tries to land anyway. The children and Dr. Smith distract the alien teens with music and dancing so John can approach in secret. John and Don arrive to rescue them, and the Jupiter 2 blasts off to continue its journey through space.
- The title of this episode is an allusion to the biblical Promised Land.
- Keith Taylor returns as "Edgar". He also played one of the orphans in "Return from Outer Space".
- Edgar has a Beatles poster on his wall.
- The Robinsons launched in late 1997, and Bartholomew claims that a Human colony has been on Delta for three years. For his story to be plausible, this episode would have to take place in 2001 at the earliest.
- The "electronic fireworks" display is the same effect as was used to show the Jupiter 2 going beyond the speed of light in "Visit to a Hostile Planet".
- Was Smith actually sick or not? If he was only faking sick, why did he refuse to eat? If he really was sick, how the heck did he get over it so suddenly?
- Why was Smith so thrilled to be given a bouquet of flowers as if he were one of the ladies?
- Why do the dance music and spotlights make John weak and dizzy?
- Who voiced the loud speaker during the brainwashing?