Lisa Genova meets 23andMe in this “extraordinary breakthrough novel” (Sarah McCoy, New York Times bestselling author) about a geneticist whose young son’s questions about his biological father lead her to track down the anonymous sperm donor she once chose, setting off a chain of events that threatens to upend their lives.

Geneticist Paige Robson has built her life on careful choices and hard-earned independence. But when her eight-year-old son, Miles, begins struggling at his new school and asking questions about his biological father, Paige is forced to confront a past she has long kept sealed away. The anonymous sperm donor she once chose suddenly enters their lives, setting off a chain reaction Paige never anticipated.

As Miles searches for where he belongs, Paige’s carefully constructed world begins to unravel. The truth about Miles’s paternity threatens her sense of security, while unexpected friendships, the reappearance of her own estranged father, and long-buried vulnerabilities push her to reexamine the meaning of family. When tragedy strikes, Paige must face the consequences of a secret only she has carried—and decide what honesty really demands.

Blending the intimacy of family drama with the intrigue of modern science, this moving novel reveals that while DNA may explain how we’re made, it cannot fully explain who we are—or who we choose to love.