During a stopover in Germany in the middle of a carefree road trip through Europe, two American girls find themselves alone at night when their car breaks down in the woods. Searching for help they find only an isolated villa, whose mysterious owner, Dr Heiter, takes them in for the night. Dr Heiter explains to them that he is retired surgeon who had specialized in separating Siamese twins. However his "patients" are not about to be separated, but joined together in a horrific operation.