The Last Detective by Robert Crais
Elvis Cole is once again coming to terms with his life as a PI on the streets of LA. He loves his girlfriend, Lucy Chenier, but his constant exposure to the Californian underclasses has stretched their relationship to the limit - especially when Cole's job brings danger too close to her beloved son. The young boy, Ben, is rapidly becoming the light in both their lives. Then one sunny afternoon, the demons from Elvis's past finally come to visit. Ben is snatched from Cole's secluded home. The kidnappers call. They don't want money. They only want retribution. But who from his past is capable of such a crime? The only clue is that the kidnappers mention the words 'five-two'. Five-two was his unit designation in Vietnam - a life he has avoided thinking about for over twenty years. Now Elvis must embark on a journey into his own past to try to protect his future. For it seems that this kidnapper is not only someone who knows him, but someone who owes him.