In the refined Madrid of the late 19th century, the enigmatic ghost of Dr Mantua reveals to the young Basilio the existence of an underground city inhabited by sinister characters engaged in criminal activities. Basilio manages to track down the tower of the seven hunchbacks, within which Inés, niece of the deceased doctor, lies kidnapped and hypnotised. A Spanish fantasy film classic based on the classic novel by Emilio Carrere.