Ghostly Echoes

"Tread lightly, Miss Rook," warned Mr. Jackaby. "It would not do to push Miss Cavanaugh too far or too fast."
Jenny Cavanaugh, the ghostly lady of 926 Augur Lane, has enlisted the investigative services of her fellow residents to solve a decade-old murder—her own. Abigail Rook and her eccentric employer, R. F. Jackaby, dive into the cold case, starting with a search for Jenny's fiancé, who went missing the night she died. But when a new, gruesome murder closely mirrors the events of ten years prior, Abigail and Jackaby realize that Jenny's case isn't so cold after all.
Fantasy and folklore mix with mad science as Abigail's race to unravel the mystery leads her across the cold cobblestones of nineteenth-century New England, down to the mythical underworld, and deep into her colleagues' grim histories to battle the most deadly foe she has ever faced.
Ghostly Echoes, the third installment in the New York Times bestselling Jackaby...