The Zygon Invasion

The Zygon Invasion was the seventh episode of the ninth series of Doctor Who. It followed The Woman Who Lived and was succeeded by The Zygon Inversion. It was first broadcast on BBC One at 8:15pm on 31 October 2015 and was forty-six minutes in length.

The story's listing on BBC iPlayer. (WC: The Zygon Isolation)

You may be looking for the real world television story.

Its synopsis stated "When Osgood is captured by a rogue gang of Zygons, the Doctor, Clara and Unit must scatter across the world to set her free".

By 10 May 2020, the episode was available on BBC iPlayer along with the rest of series 9. Petronella Osgood watched it while in self-isolation. (WC: The Zygon Isolation)