Anxious to explore the mysterious hidden world under metropolitan Berlin, an international group of four urban explorers hires a local guide, Kris, who leads them into the maze of escape tunnels and subterranean fortifications under the city. When their guide has a bad fall, two of the girls in the group frantically set off to seek help while Denis, the young American, stays behind. Armin, a former East German border guard suddenly appears from nowhere. Out of sheer desperation, Denis allows
