Contemporary, Police Procedurals, Crime 

In a secluded New York City park, a double homicide draws two detectives named McKenna. One is a legend; the other is a brilliant young investigator. Together, they are entering a case that will grow more bizarre and more horrifying with each new piece of shocking evidence...One of the victims was tied to a tree and slowly tortured to death. Veteran detective Tommy McKenna realizes that he has seen this killer's work before-eighteen years earlier...Tommy will get a second crack at his killer. Brian McKenna gets to work with a legend. And both men are setting in motion an investigation that will take them to California, Arizona, a Costa Rican mountaintop, and all the way to the Fare East. The two McKennas are on the trail of two human monsters who have been killing for two decades-and murder isn't even the worst of their crimes... - from Amzon