The Girl in the Lake by India Hill Brown
Celeste and her younger brother are being dropped off at their grandparents place lake house for a long summer week with their two cousins. But Celeste is worried. She doesn't know how to swim, and here she is ... at a lake house. But it turns out that shouldn't be her biggest worry. Because there is definitely a ghost haunting the house!
Recommended for grades 6 and up.
