At the heart of Gardner's outstanding fourth novel featuring Boston PD detective Warren (after The Neighbor) are some very sick kids, notably Lucy, a nine-year-old feral girl who self-mutilates when any attention is given to her, and Evan, an eight-year-old boy who during fits threatens to kill his mother. D.D gets involved after two grisly family annihilations lead to the locked-down pediatric psych ward in Cambridge that specializes in Lucy's and Evan's types of hard case. When a child is too sick and the parent can no longer handle care, the child ends up in the acute care facility under the tutelage of pediatric psych nurse Danielle, the lone survivor of her own family bloodbath. Coincidence? That's for D.D. to figure out--in the midst of a budding romance with police academy professor Alex Wilson and infuriating encounters with Andrew Lightfoot, resident "woo-woo expert" (that's cop talk for psychic), who works in tandem with the hospital. Plenty of red herrings keep readers guessing, but Gardner always plays fair in this tight and consistently engaging page-turner.