From New York Times and #1 international bestselling author Linwood Barclay comes the third and final spine-chilling thriller in the Promise Falls trilogy. Everything has been leading to this. It's the Saturday of Memorial Day weekend, May 23rd, and the small town of Promise Falls, New York, has found itself in the midst of a full-blown catastrophe. Hundreds of people are going to the hospital with similar symptoms—vomiting, dizziness, loss of consciousness—and dozens are dying. And those investigating the cause of the epidemic quickly zero in on the water supply. But the question for many, including private investigator Cal Weaver, remains: Who would benefit from poisoning this town? And what is their motivation? Meanwhile, as tragedies mount and the number of suspects grows larger, Detective Barry Duckworth is faced with another problem. He knows that the killer of Olivia Fisher and Rosemary Gaynor is still out there. And what's more, he knows that the mystery behind the significance of the number 23 is growing and is linked to a much larger scheme than he'd originally imagined. Detective Duckworth will have to race to put together all the pieces of this puzzle to stop someone's sinister revenge plot.