Series information from Goodreads.

"Stephen King's HOLLY marks the triumphant return of beloved King character Holly Gibney. Readers have witnessed Holly's gradual transformation from a shy and reclusive (but also brave and ethical) homebody in Mr. Mercedes to Bill Hodges's partner in Finders Keepers and End of Watch to a full-fledged, smart and occasionally tough private detective on her own in The Outsider and If It Bleeds. In this new novel, Holly once again claims the spotlight, and must face some of her most depraved adversaries yet. When Penny Dahl calls the Finders Keepers detective agency hoping for help locating her missing daughter, Holly is reluctant to accept the case. Her own mother has just died, and Holly is supposed to be taking time off. But something in Penny Dahl's desperate voice makes it impossible for Holly to turn her down. Mere blocks from where Bonnie Dahl disappeared live Professors Rodney and Emily Harris. They are the picture of bourgeois respectability: married octogenarians, devoted to each other, semi-retired lifelong academics. But they are harboring an unholy secret in their well-kept, book-lined home, one that may be related to Bonnie's disappearance. And it will prove nearly impossible to discover what they are up to: they are smart, they are patient, and they are ruthless. Holly must summon all her formidable talents to outhink and outmaneuver this brilliant and twisted pair in this chilling new masterwork from Stephen King."-- Provided by publisher.