Twenty-five years ago, the body of 16-year-old Eve Knox was found in the caves near her home in small-town Grotto, Iowa - discovered by her best friend, Maggie, and her sister, Nola. There were a handful of suspects, including her boyfriend, Nick, but without sufficient evidence the case ultimately went cold.

Everyone from Wakarusa, Indiana, remembers the infamous case of January Jacobs, who was discovered in a ditch hours after her family awoke to find her gone. Margot Davies was six at the time, the same age as January—and they were next-door neighbors. In the twenty years since, Margot has grown up, moved away, and become a big-city journalist. But she’s always been haunted by the feeling that it could’ve been her. And the worst part is, January’s killer has never been brought to justice.

When Dr. Sloan Hastings submits her DNA to an online genealogy site for a research assignment, her goal is to better understand the treasure-trove of genetic information contained on ancestry websites. Brilliant and driven, Sloan is embarking on a fellowship in forensic pathology, training under the renowned Dr. Livia Cutty. Sloan has one reservation about involving herself in the experiment: she’s adopted. Grateful for a loving home, she’s never considered tracking down her biological parents.

Your phone rings. A stranger has kidnapped your child. To free them you must abduct someone else's child. Your child will be released when your victim's parents kidnap another child. If any of these things don't happen: Your child will be killed. You are now part of the chain.

Darby Thorne is a college student stranded by a blizzard at a highway rest stop in the middle of nowhere. She’s on the way home to see her sick mother. She’ll have to spend the night in the rest stop with four complete strangers. Then she stumbles across a little girl locked inside one of their parked cars. There is no cell phone reception, no telephone, no way out because of the snow, and she doesn’t know which one of the other travelers is the kidnapper.