The return of Doctor Who's Zygons will lead into one of season 9's biggest cliffhangers.

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Last seen in the 50th anniversary special, the ever-morphing aliens will return in episodes 7 and 8. Penned by Peter Harness, this two-part storyline will have fans white-knuckling it through the weeklong break between episodes.

"It's nice to do a cliffhanger," Harness teased, according to Digital Spy. "And I tried to do the biggest cliffhanger I possibly could."

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The appearance of the sucker-clad Zygons will also herald the return of Osgood. Killed off in season 8's "Death in Heaven," the UNIT scientist will somehow manage to find her way back into the storyline from beyond the grave. It is currently unclear if the Doctor will find her as he takes a trip to the past, if Osgood will appear in the form of a Zygon courtesy of their meeting in "The Day of the Doctor," or if Harness has some other twist in mind.

"It's a bit unbelievable to be bringing [the Zygons] back again - and also Osgood as well, another fan favorite," Harness told Digital Spy. It's a privilege to be telling a story about those two, and I think it's quite an exciting story as well. Unfortunately I've got two fan favorites in my hands now, which can only set me up to disappoint people!"
Hopefully that's not the case!

Find out more when Doctor Who returns to the BBC this fall. Click the video below to see the Zygons in action.

Tags: Doctor Who television BBC