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.'

Sarah Jane Smith, on holiday with her chum Jeremy and a bad case of writer's block, is amazed to find the Brigadier in the same part of Italy. He is there to help a distant relative whose tiny island home has been threatened by American mobster Max Vilmio.
When the ghosts that haunt the island's crumbling castle are joined by less benign spectres, the Brigadier summons the Doctor — who discovers that the whole of mankind is threatened by the plans of the ruthless Vilmio and his mysterious, hooded henchman.