The Zygons, a race of shapeshifting aliens, have been living in secret on Earth, unknown and unseen – until now. When Osgood is kidnapped by a rogue gang of the shapeshifting aliens, the Doctor, Clara and UNIT must scatter across the world in a bid to set her free.

But will they reach her in time, and can they stop an uprising before it’s too late?

Humans star Rebecca Front guests in this episode.