Mystery of Hilliard's Castle

Kerry Odell and her younger brother Lyle are not enthusiastic about spending the next six months in rural western Maine. It seems like a pretty dismal place, especially in March, and means entering a new school in mid-year. The house their mother has rented, with its locked tower, has all the makings of a haunted "castle" with mysterious comings and goings, odd noises in the night, and a landlord who seems to have it in for them. Set in 1982. Reading level 4.9.
from the reviewers:
"Emerson writes with suspense and spins a clever plot. The book is full of action and shows a certain pre-teen authenticity in its portrayal of adolescent relations and concerns."
"Emerson is to be commended for realistically portraying a young girl's anxiety over the possibility of her widowed mother's remarriage, and the potential rift in the mother-daughter relationship that may ensue as an important new family member is absorbed."