What makes a psychopath? A young woman delves into her family's shadowy legacy in a terrifying novel by the #1 Amazon Charts bestselling author of Strangers We Know.

Psychology student Olivia Eriksen's family is notorious among true-crime buffs. Faced with a legacy of psychopathy that spans generations, Olivia has spent much of her academic life trying to answer one chilling question: Nature or nurture?

Although she's kept a safe distance from her blood relatives for years, Olivia agrees to attend a weekend reunion. After all, her fiancé is eager to meet his future in-laws, and the gathering may give her a chance to interview her elusive grandfather about the family traits.

But nothing is ever peaceful among the Eriksens for long. Olivia's favorite cousin is found dead in a nearby lake. Then another family member disappears. As a violent storm isolates the group further, Olivia's fears rise faster than the river.

And an uninvited guest is about to join the party. True-crime podcaster Birdie Tan has uncovered a disturbing mystery in her latest investigation--and she's following it right to the Eriksens' mountain resort. There's a deadly twist in the family plot that even Olivia doesn't see coming.