Spenser is just settling in to a new office, after his old one got redeveloped out of existence, when a new client walks in. Patty Giacomin's ex-husband has taken their 15-year-old son Paul, and Patty doesn't know where the ex-husband lives. That makes even having him served with a summons rather difficult. What she wants from Spenser is to find him, and bring Paul back home.
This does seem to be mostly about not letting her husband win.
Finding Mel Giacomin turns out to be fairly easy, and since he is also mainly concerned about winning and not much about Paul, it's not hard to convince him it isn't worth a fight with Spenser. It's not long before Spenser has delivered Paul to his mother, and that's the end of the matter.
Except it isn't.
The Giacomin elders are really messed up, and they can't seem to stop using their son as a pawn in their battle with each other. A few months after the initial event, Spenser gets a phone call from Patty, who says that thugs hired by Mel tried to kidnap Paul.
It's the first step in Spenser becoming far more involved in Paul Giacomin's life than he ever imagined.
The "detective story" aspects of this novel are fairly minimal, there only to provide Spenser a route into this quite different story. The real core of this story is in the relationship that forms between Spenser and Paul. With such lousy parents, he figures Paul's only chance at a decent life is to grow up fast, and learn to become autonomous, to the extent possible, at just fifteen. Spenser can't be a father to Paul, but he becomes, at least, a big brother. Initially with Patty's consent, because it's a way of keeping Paul out of Mel's reach, Spenser takes Paul to Maine, to Susan's property near Fryeburg, and embarks on a crash education course. He teaches Paul what he knows: weight-lifting, running, boxing, carpentry, appreciation of good food--and how to say what he wants, and to have confidence his own real likes, desires, and goals. Paul, Spenser, and Susan all have real emotional challenges to face in this excellent but somewhat atypical Spenser novel.
I bought this book.