While trying to fix the chariot, Will hears the Robot approaching. The Robot goes through its programming out loud, "Eliminate all non-essential personnel". The Robot creates an electric charge between its outstretched pincers. Will tells the Robot to go back. Back at the Jupiter 2, John and Don prepare to go to the Chariot to get Will. Smith is caught trying to slip away unnoticed. John tells him he will be in trouble if his friend the Robot causes any trouble, John noticed that the Robot will only listen to Smith's voice commands. Smith says it was a programming oversight. Will's distressed voice is heard over the radio. John, Don and Maureen rush out. Back at the chariot, Will tells the Robot to do a routine check, faking Smith's voice. The Robot complies. John, Don and Maureen reach the chariot, John sends Don to get Smith. Will verbally goes through a series of chess moves with the Robot. Smith reaches the chariot and pulls the power pack from the Robot. everyone returns to the ship.
Later that evening, John goes over his plans for the next few days, assigning everyone a certain task. In the morning John and Don work on the force field, Smith helps Judy and Penny with gardening. He plants some seeds into the planets native soil. He leaves with a soil sample for analysis. He finds Will working on the visual scanner. Smith goes to the lower level, where he tosses the soil sample and gets himself some coffee. Maureen finds him doing nothing, Smith says he is exhausted from helping everyone do their jobs. That evening John and Don test the force field.
In the morning John and Don head out to fix the chariot and bring it back. Will asks about the Robot, John tells him to leave the Robot turned off. Judy calls Maureen to check out the garden, the seeds that Smith planted have grown to giant proportions overnight. Smith cuts one of the plants open and some sort of Plant creature emerges. Will shots it with a laser gun. John and Don get the chariot fixed and head back towards the ship, John notices that the terrain seems rougher than it did before. The camera pulls out to reveal a giant alien footprint. Back at the ship, John checks cell samples from both the plant and the soil and find them to be similar in nature, neither animal or plant but a combination of both. Will decides to power up the Robot when everyone is asleep after fixing the programming. The Robot seems to be working properly. A howl is heard from far off and the Robot deactivates the force field and goes to investigate. Will yells to the Robot to come back to no avail. John hears Will yelling and comes outside. John scolds Will for reactivating the Robot and sends him to bed.
In the morning John has a talk to Will about what happened the night before. The Robot returns, babbling and Will removes it's power pack. John fill out his daily log, talking about the fast growth rate of the vegetables and why some died overnight. John and Don check the weather tracking station they set up. John find the temperature dropping quickly. He decides they must pack the chariot and move south where it is warmer. Don and John find the giant footprints, as they head back to the ship they run into a giant cyclops alien. Back at the ship Maureen cleans clothes as Judy and Penny gather vegetables. Will fixes the radio telescope and calls Maureen to check, she sees the giant alien through the telescope. Will grabs the laser gun and runs off.
John and Don duck into a cave as the giant tries to get them. Will finds the giant alien and fire the laser gun. The giant falls back, stunned. Back at the ship, John tells everyone they must leave the ship, Smith decides to stay. They pack the chariot as the temperature drops. Just before they are ready to leave, they notice Penny and Debbie are missing. John puts on the jet pack and takes off to find them. John spots them miles away riding on the back of a large turtle. She hops on the back of the jet pack with Debbie and John takes them back to the waiting chariot. They start their trek south. Their path is blocked by the giant alien throwing boulders at the chariot, Don uses the laser rifle and the giant falls dead. The boulders damaged the power unit. They set up camp while fixing the power unit.
At night Will play the guitar and sings while sitting around the camp fire. Penny dresses Debbie in a dress. Judy flirts with Don while he fixes the chariot. John helps Maureen prepare dinner. The next day they get into the chariot and continue heading south. Later that day they run into a lightning storm and drive the chariot into a huge cave. They get out of the chariot to explore the cave and find ancient alien ruins. While exploring a castle in the ruins, Debbie runs off, Will and Penny fall through a trap door in the wall and get trapped inside. Don and Judy hear them on the other side of the wall and also enter the trap door. At that moment an earthquake hits. John and Maureen hear them and try to use the laser gun to cut a hole in the wall.