The "Concordia" trading company in Würzburg is a secret headquarters of the MID, a secret service agency of the US Army. For years, espionage, sabotage, and diversion operations originated from here in order to undermine the Socialist Republic of Germany. A favorable moment for a military attack approaches and plans are developed. These plans are placed in the hands of Major Collins, who keeps them in a safe. Hansen has worked for him for many years, but also for the Stasi as a double agent. Security Chief Colonel Rock knows there is a leak, but Hansen has passed every test thrown at him. He is trying to deal with his current assignment: acquiring the plans so they can be made public. His mission is to get them out of the safe and into the GDR without getting caught.

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.