Mystery by Moonlight

Rap, rap, rap. The eerie sound is coming from the deserted house. Gail is sure of it! But no one has lived there for ages. Gail has never before dared to walk past the ghostly house by moonlight--not by herself. Why, oh why, had she run ahead of Conan and her brothers? If only she had waited for them? Then she hears it again--that hollow sound behind the ruined walls--rap, rap, rap. Frightened, she calls to the boys, "Come quick!" How can they know this is only the beginning of many strange and baffling happenings that will involve them all?