The TARDIS lands in the city of Tromesis on Earth — but it’s a world far from the one that the Second Doctor, Jamie and Zoe recognise.

The buildings are ruined, the streets deserted. And against the devastation they see a ghostly mirror image of another place — the city as it was before disaster hit.

People vanish here, and huge metal birds attack from the sky.

Can the Doctor find the future, in a place that doesn’t have one?