The near future: a man in a psychiatric hospital claims to be an alien time traveller called 'the Doctor'.  He once adventured across countless galaxies, fighting evil.

The past: an asylum struggles to change Victorian attitudes to the mentally ill.  It catches fire in mysterious circumstances.

Now: a young woman takes an overdose and slips into a coma.  She dreams of death falling like a shroud over a benighted gothic building.

Caroline 'Laska' Darnell is admitted to the Retreat after her latest suicide attempt.  To her horror, she recognises the medical centre from the recent nightmares of an old building haunted by a ghostly dog with glowing eyes.  She knows that something is very wrong with the institute.  The mysterious Dr Smith is fascinated by Laska's waking dreams and prophetic nightmares.  But if Laska is unable to trust her own perceptions, can she trust Dr Smith?

And, all the while, the long-dead hound draws near...

This is another in the series of adventures for the Eighth Doctor.