It's May 23, and small town Promise Falls finds itself in the midst of a full-blown catastrophe with dozens dead from a flu-like virus. Investigator Cal Weaver quickly zeros in on mass poisoning and a tainted water supply.

Meanwhile, a college student has been murdered, and Detective Barry Duckworth recognizes a killer's handiwork from the unsolved homicides of two women in town. Suddenly, the strange events from the last month start to add up....Bloody mannequins in car "23" of an abandoned Ferris wheel...a fiery, out-of-control bus with "23" on the back..."23" on the hoodie of a man accused of assault.

The motive for hurting the people of this town points to the number 23--and working out why will bring Duckworth closer to death than ever before.