1935. Six homicidal lunatics - the so-called 'Devil's Six' - are confined in a remote castle asylum in rural Czechoslovakia. Dr Viktor Kosárek, a young psychiatrist using revolutionary techniques, is tasked with unlocking their murderous secrets. At the same time, a terrifying killer known as 'Leather Apron' is butchering victims across Prague. What links him with the insane inmates in the asylum? A modern gothic masterpiece.