The Bad Ones by Melissa Albert

Goddess, Goddess, count to five. In the morning, who's alive?

In a single winter's night, four people vanish without a trace across a small town . . . Nora's best friend, Becca, is one of the lost. Determined to find her, Nora discovers a string of coded messages Becca has left. These clues point to another missing girl thirty years prior and a sinister urban legend: a goddess figure, who played an eerie role in Nora and Becca's own childhood games . . .

As Nora unravels the mystery, it's soon clear there are dark forces at work in her town - and they'll stop at nothing to keep their secrets buried deep.