Horror in which the exploration of subterranean Berlin by a group of urban adventurers takes a horrifying twist. The explorers, led by Kris (Max Riemelt), have been drawn to the underground tunnels and passageways of the city by its fraught and complex history. In search of the quasi-mystical 'Führerbunker', they secretly make their way into a disused tunnel system to begin their quest. However, misfortune strikes when Kris suffers a fall and becomes unconscious. Left in darkness beneath the city, with their guide seriously injured, Denis (Nick Eversman) is initially relieved when a former East German border guard, Armin (Klaus Stiglmeier), appears and offers to lead the group to safety. But what are Armin's real intentions?