Nancy, East of France. Summertime. Seeking to escape her troublesome family environment, Sophie, 15, jumps at the chance to get the spare keys to her wealthy friend Jade's house. While enjoying the spacious home she thought deserted for summer, she bumps into her friend's older brother Stéphane, who, as fate would have it, was also planning on staying. But instead of chasing her out, Stéphane will choose to leave the door open as an invitation to a summer Sophie never expected.

In the heart of a city, the inhabitants of a tower wake up one morning to find that their building is shrouded in an opaque fog, obstructing doors and windows - a strange dark matter that devours anything that tries to pass through it. Trapped, the residents try to organize themselves, but to ensure their survival they gradually succumb to their most primitive instincts, until they sink into horror...