Deep

Ben and Tina, a young couple from New York, embark on an adventurous journey across Europe. Their goal is to explore reputedly haunted locations while documenting their experiences as YouTube content creators.

Upon arriving in south-west France, Ben and Tina aim to explore a sanatorium submerged beneath an artificial lake. However, they are surprised to find the site bustling with vacationers, which shifts their initial plan.

They meet a local named Pierre, who offers to guide them to a secluded part of the lake deep in the forest of Chanteloup. Pierre informs them that this area, flooded in 1984, is rumored to house a mansion that has survived remarkably intact.

Ben and Tina dive into the lake and discover the submerged mansion. As they explore its contents, they are struck by the preservation of the items inside, raising an eerie atmosphere around their adventure.

While exploring the mansion, they begin to hear unsettling voices and noises that disrupt their investigation. They notice their drone's motion tracker picking up inexplicable movements, amplifying their growing unease.

As they delve deeper, they find disturbing photographs, posters, and articles about missing children. The discovery of satanic symbols and scratches on the front door suggests that they are not alone in the mansion.

In the kitchen, they encounter a doorway blocked by a large crucifix. After managing to open it, they are horrified to find two corpses restrained in chains, alongside a chilling satanic pentagram.

In their frantic bid to escape, they realize that the window they used to enter has been sealed with a brick wall. This discovery traps them within the mansion, heightening the tension as they search for other exits.

While attempting to pry open a grate in the cellar, Tina is suddenly attacked by an unseen force. Strangely, the assault stops and Ben dismisses it as nothing unusual, leaving Tina baffled and uneasy.

Ben uncovers the masks from the corpses, revealing them to be the Montégnac family, the original owners of the mansion. They soon realize the dangers surrounding them as the corpses animate and chase them.

In an upstairs chamber, Ben discovers a family tree that reveals Pierre's true identity: he is the son of the Montégnacs. This shocking revelation implies that Pierre lured them into a terrifying trap.

Ben becomes possessed by the ghost of Sarah, the undead daughter of the Montégnac family. Under her influence, he attempts to manipulate Tina, revealing the dark legacy of their family.

Tina discovers a hidden satanic chapel and finds a shaft leading out. In a desperate bid to escape, she confronts Ben, who is attempting to take her life, leading to a life-and-death struggle.

In self-defense, Tina strikes Ben with a knife, breaking him free from his possession. However, the victory is short-lived as Sarah fatally stabs Ben before Tina can escape, exemplifying the tragedy of the situation.

Tina narrowly escapes through the shaft but drowns as she reaches the surface, marking her tragic fate. The camera then reveals two new divers at the lake, accompanied by Pierre, suggesting a repeating cycle of horror.