Dora Henry has problems in her personal life; her nominal marriage to the cold, unemotional Jared Gerber is at an end, but she fears the consequences of leaving him. She has problems in her professional life; investigating the murder of a single local scientist, the policewoman has discovered what may be a string of related homicides. And she has a problem in her garden. A persistent weed puts her husband in the hospital, and launches Dora into a brand new life.

Sheri Tepper's The Family Tree starts like a gritty novel of a woman-on-the-edge or a murder-mystery, then twines off in unexpected directions, like rootlets seeking moisture, or vines exploring a wall. When Dora Henry encounters the strangely-responsive weed, she leaves the well-trodden path of her life and enters a dark forest. Just as we are accepting this single weird element, Tepper vaults us to a new story, the tale of Nassifeh, a sweet Ponjic teenager called "Opalears" by the other girls in the Sultan's harem. She masquerades as a boy named Nassif to accompany the Scuinic son of the Sultan, Prince Sahir, on his quest to visit the sages of St. Weel and save "all posterity."

Along the way, they encounter Sitidic, Pheledic, Armakfatidi and Onchiki people, and we learn that this is a future Earth. Some people (like the Dire Duke Fahsahd) have descended to cannibalism, but others are identifiable by their enduring "national" qualities. The Ponjic people, like Nassif and Prince Izakar of Palmia, who has access to one of the few remaining libraries, may be "Joosh" or perhaps "Mericans"—at least Izakar thinks so, based on his reading. Armakfatidi may once have been the "Frynch"; they are touchy, but very good cooks, and their language is described as "grummeling." The Scuinic people like Prince Sahir are probably "Ahraban," the Pheleds like Sahir's gracefully-powerful bodyguard Soaz may be "Zhapanees."