Mark uses the final clue from Rose's letter to discover that beneath each floor is a secret crawl space. He follows hidden passages to a suite of rooms where he finds Professor Arnold who reveals, via an electronic voice generator, that he is in fact Varelli. He tries to kill Mark with a hypodermic injection. During the struggle, Varelli's neck is caught in his vocal apparatus, choking him. Mark frees him, only to be told that he is still being watched as Varelli dies. Mark follows a shadowy figure to a lavishly furnished chamber, where he finds Varelli's nurse. Laughing maniacally, she reveals to him that she is Mater Tenebrarum. She vanishes, but re-emerges through a mirror as Death personified. However, the fire that has consumed much of the building enables Mark to escape from the witch's den. Debris crashes down on the fiend, destroying her.