Masha Gessen's mother had a fatal flaw: a genetic mutation that put its carriers at very high risk of ovarian and breast cancer. After her mother died, Gessen discovered that she carried the same mutation. But what do you do with this kind of knowledge? Gessen, a journalist and ex-war correspondent, set out to discover more. Travelling the world, Gessen meets with scientists, psychologists and economists, and encounters whole communities touched by the effects of defective DNA. Her decision about her own future becomes another part of her journey, revealing how genetic information is transforming our most basic sense of who we are.