Hundred-Dollar Baby is the 34th Spenser novel by Robert B. Parker. The story follows Boston-based PI Spenser as he tries to help an old runaway prostitute he helped several years earlier, April Kyle.
April Kyle appears in Spenser's office after several years without any contact. She's been put in charge of a new upscale brothel by her mentor, the madame Patricia Utley. She says she's being harassed by someone who wants her to pay an extraordinary protection fee. Thugs appear and scare off her customers. Spenser and Hawk manage to fend off the thugs, but things are not as they seem as soon as Spenser starts asking questions. April begs him to stop investigating, but, Spenser being Spenser, can't stop until he unravels the mystery. What surfaces is a web of deceit, greed and the fragile psyche of April Kyle.