While diving in a remote French lake, a couple of YouTubers who specialise in underwater exploration videos discover a house submerged in the deep waters. What was initially a unique finding soon turns into a nightmare when they discover that the house was the scene of atrocious crimes. Trapped, with their oxygen reserves falling dangerously, they realise the worst is yet to come: they are not alone in the house.
A sawmill owner and his teenage daughter become tangled in a deadly feud when a drug dealer stashes stolen cocaine on their remote property.
When the disappearance of children and bloody murders multiply in a small mountain village, an old legend shrouded in sulphur reappears... Commander Guardiano and Captain of the Gendarmerie De Rolan are forced to join forces to uncover the truth.
