The summer of 1960 was the hottest ever for Summit, Wisconsin. But for Frankie, Viv and Biz, 11-year-old best friends, it would forever be remembered as the summer that evil paid a visit to their small town. With a to-do list in hand, the girls set forth from their hideout to make their mark on that summer, but when three patients escape from Broadhurst Mental Institution, their idyllic lives take a sinister turn. Determined to uncover long-held secrets, the girls have no idea that what they discover could cost them their lives and the ones they hold dear. Six decades later, Biz, now a bestselling novelist, remembers that long-ago summer and how it still haunts her and her lifelong friend.