The Elementals by Michael McDowell

After a bizarre and disturbing incident at the funeral of matriarch Marian Savage, the McCray and Savage families look forward to a restful and relaxing summer at Beldame, on Alabama's Gulf Coast, where three Victorian houses loom over the shimmering beach. Two of the houses are habitable, while the third is slowly and mysteriously being buried beneath an enormous dune of blindingly white sand. But though long uninhabited, the third house is not empty. Inside, something deadly lies in wait. Something that has terrified Dauphin Savage and Luker McCray since they were boys and which still haunts their nightmares. Something horrific that may be responsible for several terrible and unexplained deaths years earlier - and is now ready to kill again