The final book in Octavia Butler's excellent Xenogenesis trilogy. Jodahs, the child of an Oankali/human family, is growing up not to be male (as it expected) or female, but ooloi, the third Oankali sex and a powerful natural genetic engineer. The power of the ooloi coupled with the unpredictability of humans scares the Oankali community, and it is exiled with his family until it can be seen if it is safe to be around - an out-of-control ooloi could cause massive damage to other living creatures around it. On their wandering exile, Jodahs discovers a band of resister humans who are somehow still fertile without being joined to Oankali families - and who are massively inbred. Jodahs learns to use its abilities to help heal them - and becomes the centre of a race-wide debate about what to do with them.