A young sheriff's deputy, Zoe Adams, investigates a series of murders and soon realizes a serial killer is on the loose. As she and her boss, sheriff Jimmy Fleck, feel the pressure of finding the killer, their love affair begins to falter. Meanwhile, Zoe teams up with the autistic bloodhound trainer, Leroy Calhoun, and together they start connecting the dots between the killer's mysterious clues. With Zoe's determination and Leroy's amazing mathematical talents, they eventually solve the riddle and track down the ingenious murderer. But when Zoe learns that she is the ultimate object of the killer's obsession, will the dysfunctional Leroy be able to save her before it's too late?