I first read this when I was a teenager.

In the previous book, the Oankali rescued some humans, made them long-lived, but rendered them infertile with each other. The Oankali are obsessed with genetics, trading good genes. Most of their equipment is actually living, even their spaceship. Humans can no longer breed in a binary fashion - they must engage a third neuter Oankali partner who mixes the genetic material for a baby. The rescued humans were kept on a spaceship until they were ready to work with the Oankali and until the Earth had been restored.

The Earth has been restored by the alien Oankali after a nuclear holocaust. The villages set up by the Oankali to house the Oankali and humans are actually baby spaceships, which will take a large part of the Earth's surface with them when they mature, leaving the Earth mostly lifeless, but this is in the future.

In this book, Lilith is the first human who gives birth to a male human-Oankali cross with 5 parents (two males, two females, one neuter, two human, three Oankali) - Akin. Many humans do not accept the need to work with the Oankali, so leave to form resister villages. Some of them do not believe they will remain infertile if they keep away from the Oankali for long enough. Others believe that the most human-looking of the human-Oankali children will be fertile together when they grow up without needing an Oankali to assist.

Akin is one of many human-looking children who are kidnapped and sold to resister villages. As a result, he does not get to grow up with people like him, but only with old humans who have no idea about his adolescence. Eventually, just before he is due to become an adult, his family find him, and send him up to the Oankali spaceship. Whilst there, Akin campaigns to restore binary fertility to resister humans, and to move them to Mars to avoid the destruction of the Earth's surface when the baby ships mature.

Something I did not notice when I was a teenager - there are no gay people in this book. People who stay with the Oankali feel disgusted when they try to touch eachother sexually - even with an ooan (neuter) Oankali, they can only touch the ooan not themselves.