A serial killer who targets twins is loose in New Orleans in this psychological thriller by the #1 New York Times bestselling author of Left to Die.

Years ago, Detective Rick Bentz helped put away the notorious serial killer known as 21, who targeted twins about to reach their twenty-first birthday. With merciless precision, 21 would arrange for his victims to die, simultaneously, at the time of their birth. But Brianna Hayward—a New Orleans woman still reeling from the murder of her twin sister—is certain the wrong man is in prison. She's willing to do anything to convince the police, even if it means trusting a reporter who's hiding his own secrets.

Now Bentz will finally have to face the terrifying possibility that 21 is still at large. Twin sisters from All Saints College have just vanished—on the eve of their twenty-first birthday. And as Bentz and his partner, Reuben Montoya, desperately follow the trail, a killer prepares to unite his next victims in death forever.