Grady Lake - Grady Lake Mystery Series, #1

Sometimes the darkest secrets are just beneath the surface  Two missing girls. One lake. Twenty years apart.  Katie Benard reluctantly returns home to Grady Lake two decades after her older sister Malorie disappeared without a trace, a story that has captivated the nation since the day she was reported missing in 2003. After leaving home years ago, Katie is overjoyed to reunite with her childhood best friend and cousin while working for her family's lakeside resort at the end of tourist season in northern Michigan.
Just when life begins to feel normal again, a teenage girl goes missing from the resort. She has vanished without a trace, just like Malorie.  The area hasn't seen a major crime in decades, leading everyone to believe the disappearances must be connected. Which scenario is more terrifying: the theory that there are two monsters lurking in this small lakeside town, or the possibility that the same maniac has waited twenty years before striking again?  This unputdownable mystery from the bestselling author of Delta County will have you guessing until the very last page.