I had always believed my father capable of a massacre. Whenever I heard on the news that there had been a killing spree, I would hold my breath, unable to relax until it was clear that it couldn’t have been him.

Randolph Tiefenthaler insists he had a normal childhood, though he grew up with a father who kept thirty loaded guns in the house. Now he has an attractive, intelligent wife and two children, enjoys modest success as an architect, and has just moved into a beautiful flat in a respectable part of Berlin. Life seems perfect—until his wife, Rebecca, meets the man living in the basement below.

Their downstairs neighbor is friendly at first, but soon he starts to frighten them—and when Randolph fails to act, the situation spins dangerously out of control.