Into the Water by Paula Hawkins

A single mother turns up dead at the bottom of the river that runs through town. Earlier in the summer, a vulnerable teenage girl met the same fate. They are not the first women lost to these dark waters, but their deaths disturb the river and its history, dredging up secrets long submerged.

Left behind is a lonely fifteen-year-old girl. Parentless and friendless, she now finds herself in the care of her mother’s sister, a fearful stranger who has been dragged back to the place she deliberately ran from—a place to which she vowed she’d never return.

Beware a calm surface—you never know what lies beneath.