Don and Judy work on insulating the water conversion unit. As Penny and Maureen set the table for lunch, an earthquake hits. Don sends Judy back to the ship as he quickly secures the water conversion unit. Just as he is leaving, a huge boulder falls in his direction. Don dives between a few large rocks.
The quake is over quickly and John rushes to help Don. As the dust settles, Don seems to be fine but his foot is wedged under the boulder. John uses a lever to free Don's foot. John brings Don into the ship and writes in his log, noting the planets orbit brings them close to the sun, causing a water shortage. John helps Don with the water conversion unit. Don tells John they have about 24 gallons of water, enough for about 2 weeks. After John checks the water tank he finds only 2 gallons of water. Don and John hear Smith singing and find him taking a shower. They yell at him for using up all the water during a draught. The tell him to get dressed and be back at the ship soon for a meeting.
At the meeting John informs everyone that the water conversion unit can only produce 1 pint of water per day, so they have to go looking for a new water supply. While on the hike, Smith says he can't go on any further, John sends him back to the ship. They soon find a source of water but it is undrinkable, however floating in the water is some alien fruit. John takes some of the alien fruit back for analysis. Debbie takes one of the fruits while no one is watching and eats it. Back at the ship, Don and the family gather around John as he conducts tests on the fruit, he says it will be at least 36 hours before he knows the results.
Maureen goes to check up on Smith and finds him outside the ship eating the alien fruits. Maureen tells him they may be poisonous. Smith blames John for leaving them out where he could find them. Smith believes John wanted to poison him. Smith runs off to his cabin. John says they must wait for Smith to develop symptoms before they could treat him. Smith decides to get revenge. When Maureen goes to check up on Smith she finds his cabin empty. Everyone goes out looking for Smith. Later that evening Don and John check the fruit analysis. Judy, Maureen, Penny and Will begin to miss Smith.
John discovers that the fuel cell is missing from the water conversion unit. Smith took the fuel cell as revenge. John, Don and Will go looking for Smith again. Back at the ship, Maureen, Judy and Penny find that Debbie has grown to giant Smith has also grown to giant John, Don and Will soon come across Smith. Smith pulls a tree from the ground and throws it at them. Will tries to persuade Smith to come back to the ship. Maureen goes to talk to Smith. Smith feels like a freak. Smith agrees to go back to the ship. That night a rain storm rolls towards the ship. The rain shrinks Smith and Debbie back to their original Smith grabs Debbie and brings her back into the ship.
The next day Judy finds Smith sitting, watching the sky for someone to rescue them. As Judy leaves the Robot detects an alien object approaching. A small alien robot probe heads towards Smith.