Still recovering from the traumatic events of the past year, newlyweds Aggie Malone, police chief of Dogleg Island, and Deputy Sheriff Ryan Grady are looking forward to a casual day trip to Wild Horse Island, a nearby nature preserve, with their precocious - and uncannily perceptive - border collie, Flash. But when Flash discovers a body in a shallow grave on the island, and Aggie and Ryan learn of an attack on the park ranger, a tangled knot of conspiracy, murder and deception begins to unfold.
Fifteen hundred miles away, an ex-con and a 15 year old girl embark upon a crime spree that will earn them the nicknames "Bonnie and Clyde". As they make their way inexorably south, Aggie, Grady and Flash are thrust into the middle of a murder investigation that leads to the arrest of one of their neighbors and the attempted suicide of another. When a search of the dead girl's belongings reveals a priceless emerald bracelet and two of the island's most popular residents go missing, the puzzle becomes even more complicated. Grady and Aggie struggle to put all the pieces into place while Flash, ever obsessed with understanding the human condition, wrestles with a more painful dilemma: how do you tell the good guys from the bad guys when they are so often the same person?