The Aggrieved
"The unthinkable has happened. A life has been extinguished--one belonging to someone Jonathan Quinn and his partner Nate care about more than almost anyone else in the world. Those responsible will pay. No matter how long it takes, no matter how far and wide the search, Quinn, Nate, and their colleagues will stop at nothing to exact the appropriate justice. Because if there is one thing those in the shadow world should know, you do not mess with Quinn's people" -- summary from amazon.com