A middle-aged couple, La Farge and his wife Anna, have moved to Mars as part of the colonization effort. One night, they are sleeping and La Farge wakes up when Anna suffers from a nightmare. She admits that she misses the rain of Earth, and he agrees with her. As he looks out he wonders about their son Tom, and Anna says that they should have brought him with them. La Farge points out that Tom has been dead for five years, but is still in their hearts. They miss driving to see Tom's grave, but La Farge says they've made their choice and there's nothing they can do about it.
The couple dozes off, but La Farge wakes up when he sees a glowing light at the window. A voice in his head tells him to let him go, and that it's been caught by him. La Farge hears someone at the door and goes to answer it, and finds his dead son Tom waiting for him. Tom says that he's come there to be with him, and he cannot go. He then goes to wake up his mother.
The next morning, La Farge finds Anna making breakfast for Tom, who knows everything that the real Tom would know. Anna doesn't find anything unusual about her son coming back from the grave, but La Farge is suspicious. Tom talks to him privately and says that he's now trapped by La Farge and Anna, and that he needs La Farge to want him there. La Farge realizes that "Tom" is one of the few surviving Martians, who were rumored to be telepathic shapeshifters. Tom begs him not to stop believing in him, and warns that if he disappears, it will hurt Anna. Tom runs off and Anna objects, no longer aware that her son ever died. However, they're too late to stop Tom from fleeing into the nearby colony town. La Farge goes into the colony but is unable to find him.
Later, Tom returns and warns that he was almost trapped by the memories of the other colonists. When he wonders if La Farge accepts him, La Farge finally gives in and the family is happily reunited. They have dinner and Anna insists that they go into town afterward so the townspeople can see their son. Both Tom and La Farge realize the problem and try to discourage her, but Tom has no choice but to agree to keep her happy. However, he insists that the couple keep him close.
As they enter the colony, a worker, Saul, meets them. He tells them that another colonist, Connors, saw a man that he had murdered several years ago. Guilt-stricken, Connors went to his home and killed himself. As they enter the colony, Tom grows increasingly worried and tries to get Anna to go back. She refuses, and La Farge wonders if Tom was the man that Connors saw. Before Tom can answer, several drunks pull him away and La Farge loses him in the crowd. He does see a young girl running to her surprised parents. She turns and glares at La Farge, and then goes off with her parents.
Tom follows the family home, and runs into his friend Charlie. Charlie explains that the Spauldings lost their daughter Lavinia in the Martian desert a year ago, but she has returned to them. As La Farge watches, "Lavinia" comes out of the house and tells La Farge to go away. He begs her to come with him, calling her Tom. The Martian reminds La Farge that he promised to keep him close but broke his promise, but La Farge insists that Tom was happy with them, and that Anna can't survive without him. The Martian begs him to stop but is then ensnared in the man's memories again and transforms back into Tom. He has no choice but to go with La Farge.
As the Spauldings look for their daughter, La Farge tries to get Tom out of town. They become separated in the crowd and Tom is caught in the memories of all of the colonists. He tries to crawl to Anna, his face changing with each memory that passes through him. Finally he is unable to maintain what little identity he has, and dissipates in a burst of light. La Farge takes Anna away, as she admits that she was glad to have her Tom back for a little while... no matter the cost.