On October 31st, 1984, Billy Parish's usual Halloween tradition of watching horror movies with his friends is interrupted when the girl next door climbs in through his bedroom window. Sporting a black eye and a face full of vengeance, Corey Henderson convinces them to help her get revenge on her boyfriend. It was only supposed to be a prank, a simple night full of trick-or-treats, but it would end in a terrible incident that would lead Billy Parish and his friends down into the watery depths of Boom Hall, where all manner of horrors awaited them. William Parish swore never to go back to Hydra Falls. But when he receives a strange call from his old friend Michael Cohen in the dead of night ten years later, a boy whom he hadn't spoke to or seen since that eerie summer, he's left with no other choice but to return. Once reunited with all his childhood friends and the horrors they'd all tried to escape so long ago, William and the rest set out to uncover the horrible history and mystery of the Howles of Boom Hall, before they join them at the bottom of Cold Soup Creek forever.