The ninth installment in Reed Farrel Coleman's series featuring Moe Prager, an ex-cop turned private detective, finds the protagonist wracked with guilt over the death of his girlfriend, Pam. Moe says guilt is a permanent infection: The thing you've done to bruise the universe may fade, but the guilt never does. The daughter's name is Sloan, but a decade earlier she'd been an Internet sensation as "The Hollow Girl," captivating audiences with soul-searching videos about her own life and hurtful attacks on her mother. Moe attacks the high-tech mystery with old-fashioned shoe leather while contending with both his guilt and his confusing feelings about the Hollow Girl's mother. If so, the novel is a fitting conclusion to this intelligent, literary series by a fine writer who has made his reputation both as a mystery writer and a poet.