THE SECRET OF SHADOW RANCH by Carolyn Keene

Nancy Drew arrives in Phoenix, Arizona, eagerly looking forward to a fun-filled vacation at Shadow Ranch, but abruptly finds herself involved in a baffling mystery. The ranch is being haunted by an unknown enemy. Local people believe that the ghostly animal is carrying out the curse of Dirk Valentine, the romantic outlaw who was killed many years ago at Shadow Ranch, where he had gone to fulfill a promise to his sweetheart. Aided by her friends Bess Marvin and George Fayne, Nancy comes face-to-face with disaster when she is trapped inside a building that is toppled by a rockslide a rockslide which is deliberately caused. But the pretty titian-haired detective remains undaunted in her determination to solve the mystery."