In failing health, widowed patriarch, Joe Bickham looks forward to opening his family's summer cottage and spending the Memorial Day weekend catching-up with his sons, Michael and Gabriel, and their broods. Over his breakfast the morning of departure, his reverie is interrupted by the crashing of a massive roiling storm. Regardless, he thinks how everyone will enjoy the cook-out dinners, lake fishing, holiday fireworks, and the traditional croquet tournament. During the drive to the cottage, the storm seems to follows him. Upon arrival, what greets him is beyond his ken. Joe tries to explain away unworldly signs and events by ascribing them to the area's folk lore. An enigmatic character, Amon, is introduced as a distant family member. He and Joe's younger granddaughter, Agnes, make ready the fireworks to announce the beginning of summer. At night, the oldest and youngest members of the family go missing. The search for them is frenetic. The result is unfathomable.