This is a modern morality fable. Following the deaths of their parents, Gaia and her sister Maya are fugitives from their village known as the Enclave. They reach a refuge known as Sylum. One attribute of Sylum is that after being there for two days everyone catches the acclimation sickness, which means that they can never depart.
In Sylum the system of social organisation is ruthlessly matriarchal. A man for example who kisses a woman other than his wife is automatically accused of attempted rape, whether or not the woman consented. Women however are encouraged to have as many children as possible, since there is a shortage of young males. Any woman who chooses not be a child-bearer is known as a Libby and becomes a social outcast.
A boy whom Gaia loved in the Enclave, Leon, comes in search of her to Sylum. Like all newcomers Leon is imprisoned when he arrives, to remain there until the ruler – the Matrarc – decides whether he is dangerous. Leon does not initially pass the test to be released, until his athletic prowess earns him freedom. Every month the community stages an athletic contest for the males, a kind of mirror image of a beauty contest. The winner of the games earns the right to choose any female who must live with him for a month in the Winner’s Cabin. Leon of course wins and chooses Gaia’s little sister, a baby whom he must care for rather than a sexual partner. The story from this point onwards revolves around Gaia’s choice between two men, and the ramifications of her choice for the Sylum community.
The reader is never quite persuaded to enter O’Brien’s imagined world, in part because of the novel’s slow pace. The rules of life at Sylum are complex and the reader learns them at the same time as Gaia, and in the same fragmented and inconsistent way, dissipating possible tension and suspense.