Four Days: The Revenge (Book 3 Days Trilogy)

It's all a game for Marquit, but one problem—he enjoys killing people for the sport. Agent Mike Ramsey has to stop him before he kills more people. Marquit gives Mike clues throughout the game, and if Mike doesn't solve the riddles, another person dies. The ultimate kill will be someone close to the team. Mike has four days before Marquit gets his final revenge.