The Ghosts of N-Space

"When the barrier gives way, this planet will be flooded by all the evil in N-Space; and at the moment I have no idea how to stop it."

The Brigadier's ancient great-uncle Mario seems unsurprised by the spectres which haunt his even more ancient Sicilian castle. But when the Doctor comes to investigate he finds himself faced with a danger as great as any he has yet encountered.

Is the answer to be found in the past, in the corrupt alchemy of the black-hearted sorcerer said to have walled up alive for his evil deeds? Or must the Doctor — and the faithful Sarah Jane Smith — brave the realm of ghosts and face the very fiends of hell?