The Lakeside Murders - Victorian Mansion, #2

The butler did it, or maybe he didn't. It's summer, and fourteen-year-old Mary Ann Markham is bored. Then she remembers that her wealthy grandfather just happens to own a rather rundown lake a short distance down the hill from his huge Victorian mansion. She enlists her live-in writing coach, Art Parker, and her friend, Jennifer Martin, to help restore the lake and its surroundings to a thing of beauty, using Grandfather's money, of course.
Things get off to a good start-that is until they discover the decomposing body of a teenage girl in the woods. Then there's the butler who likes to stargaze, the local youth hostel that just happens to catch fire while Mary Ann and Art are attending a sing-along there, the two bodies discovered in the ashes of the hostel, and the local sheriff who thinks everybody's guilty of something. While fishing from a boat on the lake Jennifer hooks something big-you guessed it-the nude body of another teenage girl.
Suspects abound, but especially the new butler, gardener, and housemaid. Time passes. The girls throw a Halloween party at the mansion for their classmates and then disappear. Now Art, with little help from the local sheriff's department, must try to find them and their abductor before they join the growing list of corpses.