On an unnamed alien planet, a group of humans (referred to as Terrans) live in a protected community called the Preserve, along with a segment of the ruling alien race, the Tlic. The Tlic, who are large, intelligent, centipede-like beings, are parasitic and need host animals for their eggs. Since the Terrans are ideal hosts, the Tlic of the Preserve have formed an arrangement with them: the Tlic offer protection and the Terrans offer one male from each family to serve as a host to Tlic eggs. The Tlic and Terrans have formed an interdependent relationship around this arrangement, and live peaceably amongst each other.
An adolescent Terran named Gan, who is mated to a female Tlic named T’Gatoi and will soon be implanted with her eggs, is visiting his family at their home. Gan and his family are drinking sterile Tlic eggs, which for Terrans have a narcotic, pleasant effect, while T’Gatoi sits with them and talks. Gan’s mother, Lien, initially refuses to drink the egg until T’Gatoi pressures her to, chiding her for suffering needlessly and allowing old age to take her earlier than it has to, since the eggs also have a life-prolonging effect on Terrans. Gan’s father frequently drank eggs and lived to twice his natural lifespan, bearing three clutches of Tlic eggs and siring four Terran children.
While they are sitting, Gan reflects about how T’Gatoi, as ruler of the Preserve, protects all of the Terrans from the masses of Tlic, and how they are all indebted to her. Indeed, Gan was promised to T’Gatoi out of the gratitude of his mother before he was even born.
T’Gatoi senses that something is wrong and rushes outside, finding Bram Lomas, a Terran who has also been impregnated by a Tlic and whose eggs are ready to hatch. He is in great pain and great danger—if the eggs are not removed before the gestating Tlic eat through their egg shells, they will begin to eat their Terran host from the inside out. T’Gatoi orders Gan to go call for help, but he argues that he should stay to help her; instead, Qui, his older brother should call for help. T’Gatoi relents and sends Gan to go slaughter an animal for the Tlic hatchlings to eat once they are removed from Bram Lomas’s body.
As Gan does so, he realizes that he is afraid to participate in the process that is about to happen, but events are by this point moving to rapidly for him to back out. He returns to T’Gatoi with the dead animal to find that she has stripped Bram Lomas’s clothing off and is securing his legs. Bram Lomas is still awake, unable to be fully sedated without killing the eggs that are living inside of him. Although Bram Lomas’s Tlic mate should have performed the procedure, she is nowhere in sight, so T’Gatoi is forced to do it herself.
Using one of her claws, she cuts open Bram Lomas’s belly and begins retrieving the Tlic grubs out of him. Bram Lomas is screaming in pain, and though Gan understands that what is happening is unavoidable, he feels as if he is helping T’Gatoi to torture the man. T’Gatoi is unbothered by Bram Lomas’s pain and wholly focused on the job of retrieving eggs from his body, licking the blood off of them as she works. Seeing that Gan is horrified and sickened, however, she sends him outside to vomit and catch his breath,
Gan does so and begins to wander off, not sure of where he is going. He happens upon Qui, who has sent word to Bram Lomas’s Tlic mate. Qui starts pressing Gan for details of what happened, but Gan is mostly unforthcoming. Qui reveals that he too saw a birthing process when he was young, but the one that he witnessed was far more disturbing: an impregnated man was also ready for his eggs to hatch, and though his Tlic mate was there with him, there was no secondary host animal for the Tlic grubs to eat once they were removed from the Terran host, meaning that they would die. Rather than saving the Terran but risking her young, the Tlic refused to open the man up and instead let her offspring eat him alive. Eventually, the Terran begged the Tlic to kill him by slitting his throat. The Tlic grubs then ate their way out of his corpse.
Gan is horrified by this story and by the birth that he just saw, plagued by visions of Tlic grubs engorged with blood climbing through human flesh. His former trust and affection for T’Gatoi turns to revulsion and fear. Though he tries to leave, Qui will not leave him alone. Qui himself hates the Tlic, having tried to run away until he realized there was nowhere to go. Qui also knows that so long as Gan is safe, he himself will never have to be a host.
After a brief fight with Qui, Gan returns to the house, arriving late in the night. The house is mostly empty, and he goes into the kitchen alone and removes his father’s contraband rifle from its hiding place. Though he had intended to clean it, he loads it with ammunition instead. T’Gatoi finds him in the kitchen with the rifle. She knows that he is upset, admitting that that is not how the birthing process was supposed to go and that Gan should never have had to see such a thing. T’Gatoi sees the rifle, and though she thinks that perhaps Gan means to kill her with it, he puts the gun to his own head. He bemoans the fact that he was never given a choice in the matter of bearing T’Gatoi’s eggs and that he does not want to be just her host animal. The act of suicide seems to him the only way to make a choice for himself. He demands that T’Gatoi ask him not to follow through.
T’Gatoi offers to impregnate Gan’s sister, Xuan Hoa, instead. Xuan Hoa likes T’Gatoi and would be willing. Gan initially accepts the offer, but quickly realizes that he is only using Xuan Hoa, whom he truly loves, as a shield in the same way that Qui uses him. As T’Gatoi is leaving to go to Xuan Hoa, Gan stops her and insists that she impregnate him as had always been planned. T’Gatoi wants to confiscate the rifle, since it is illegal and poses a threat to her future children, but Gan demands that she leave it in the house, even though that makes her afraid. Gan insists that T’Gatoi accept the same risk that he is accepting, and that she treat him as a partner and an adult, rather than as a subject or as property. T’Gatoi eventually consents, relinquishing control and accepting the risks to show that she is willing to trust Gan.
They both go to Gan’s room. He undresses and lies with her, and she implants an egg in his abdomen. As they are lying there together, Gan admits that he did not truly hate T’Gatoi, but he was afraid of her and what she would do to him. He also admits that he was afraid of losing her or letting her go to someone else; he wanted her for himself. T’Gatoi is pleased with this and promises that she will never leave him alone the way that Bram Lomas was left alone. She will protect him.
