Bullet To The Head (Liam Quinn Mystery)

A code of silence. A private eye who won't quit. A fiendishly clever homicide...
A homicide detective is cut down on his last day on the job by a sniper. The obvious suspect is a Philadelphia mobster with a long-standing grudge. But the detective had secrets, and so did his friends. The pieces don't quite add up. And Liam Quinn owes him the truth....
Former cops seem to know what the victim was up to; but they're not talking, respecting the 'Thin Blue Line' that separates law enforcement from the public. But a second victim loosens lips; can Quinn catch a killer, or has he chosen the wrong side?