Luke, Connor, Thea and Violet spend their first holiday together alone in their father's house in the south of France. The boys don't really know him, and they don't really know their half-sisters, either. Luke, the most easy going of the four, is keen to bring a new shape to their overlapping, unconventional family; Connor and Thea, born just six months apart but a world of difference between them, are struggling to hide their attraction to each other; Violet, the youngest, is trying to figure some things out about herself, and trying desperately to forget others. Sex in all its multiple forms is on the minds of the siblings during the hot, lethargic summer days spent next to the pool, but the land around them is starting to respond to something inexplicable and eerie. Animals begin to act strangely. There is a buzzing sound that only Connor can hear, and when Violet one night sees a plane light abruptly disappear in the sky, it signals the beginning of something that threatens so much more than their turbulent holiday.