The Ruin by Dervla McTiernan

I was up till 3:30 finishing this novel. The title says a lot. A bilingual triple entendre, the word ruin has a couple of meanings in Irish, as the author explains in a note. It can mean a secret, a hidden thing, but has also long been used as a term of endearment. All three meanings are evoked in this tale of tragedy and secrets and distrust. Author Dervla McTiernan handles harsh material well, portraying the bureaucratic and personal dysfunction in police and social services, as well as the desperately hard lives of children who are or should be taken into care.

Jack's apparent suicide is really a murder: he's caught witnessing a nefarious deed. On the face of it, what ties the dead man to his killer seems to be pure chance. But the killer was also a foster child -- one whose reaction to early trauma is utterly different from Jack's.