The host

Melanie "Mel" Stryder is one of few "wild" humans - rebels who have evaded the alien souls that have taken over the Earth. With her younger brother Jamie and the man she loves, Jared Howe, Mel is on the run from aliens, called souls, who hunt down humans in order to use their bodies as hosts. Souls are creatures that rely upon host bodies to survive. After "insertion" into a human body, they erase the human occupant and establish a claim over the body and mind. Wanderer is a soul who has lived on eight different planets previously, with Mel being her ninth host body. Upon waking inside her new body, Wanderer is shocked by the power and vividness of human emotions, memories, and senses, and quickly learns that Melanie is not willing to give up the entirety of her mind.

The Seeker, who is in charge of Melanie's body, starts to worry about Wanderer's apparent lack of control over Melanie's mind. Wanderer is bombarded with Melanie's memories and her powerful yearning for Jared and Jamie, and soon finds herself feeling strong love for Melanie's former companions. She becomes desperate to find out whether they are still alive. On a road trip to Tucson, Melanie remembers her Uncle Jeb telling her about a secret hideaway he once made, and which Jared is aware of. Wanderer sets out to find the hideaway, with a vague sketch of the path from Melanie's memories, and is found by Jeb on the verge of death. She is taken to the hideaway, a complex of caves in which a group of rebel humans live, but is treated spitefully as they consider Wanderer a parasite in Melanie's body. Many of the humans believe she should be put to death and attempts are made on her life, most notably by Kyle O'Shea, despite the protection provided her by some of the humans, including Ian, Jeb, and Jared (who experiences powerful, conflicting emotions towards his alien-possessed lover). Over time, Wanderer, now becoming known as "Wanda", becomes a part of the group's routine by working, eating, and becoming an unofficial history teacher by telling stories after evening meals about her experiences in former hosts on other planets occupied by the souls. During this time, Ian, Jamie, and many other humans befriend Wanda. The Seeker, still not convinced that Wanderer was killed in the desert, returns in a helicopter, but is unable to find the caves. Kyle tries to kill Wanda by throwing her into a boiling hot, underground river. Due to Wanderer's vigorous defense, he is unsuccessful and is about to fall into the river himself when his intended victim saves him. A tribunal is held and it is decided that Kyle is allowed to stay, though many of Wanda's friends are upset about this decision, particularly Ian, who believes that Kyle deserves to die after his plot to kill Wanda. Meanwhile, Ian begins to fall in love with Wanda. After discovering this, she is confused with her own feelings since she has been deeply infected by Mel's love for Jared.