The BBC has released the official story details for the seventh episode of Doctor Who‘s new season, which features the return of Ingrid Oliver as Osgood.

Written by Peter Harness (‘Kill the Moon’), ‘The Zygon Invasion’ will air at 8.15pm on Saturday 31 October on BBC One.

The synopsis reads: “The Zygons, a race of shapeshifting aliens, have been living in secret among us on Earth, unknown and unseen – until now!

“When Osgood is kidnapped by a rogue gang of Zygons, 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?”

Doctor Who executive producer Brian Minchin teased last month: “Some rogue Zygons are trying to destabilise the peace and start a war between Zygons and humans. We’ve gone global on this with stories split across the world.”

Showrunner Steven Moffat has also confirmed that “‘The Day of the Doctor’ acted as a prologue to [this story].”

> Buy Season 9 on DVD on Amazon.

> Buy Season 9 on Blu-ray on Amazon.

Season 9 continues this Saturday on BBC One with ‘The Girl Who Died’.

> Here’s everything we know about Season 9 so far.

Are you looking forward to ‘The Zygon Invasion’? Let us know below…