Footsteps on the Stairs — C.S. Adler

Fun loving Dodie is at a creepy beach house to get to know her neat little stepbrother and her cool, perfect stepsister, Anne. Anne is thirteen, like Dodie, but they couldn't be more different. When both girls hear footsteps on the stairs at night, they are thrown together to solve the mystery. Their investigation lands them in the middle of a jealous quarrel between two long dead sisters. How can Dodie and Anne pacify the ghosts?