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 at 8:15pm on 31 October 2015 and was forty-six minutes in length.
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". The opening scene featured opening captions that read "Once upon a time... when Planet Earth was in lockdown there was 3 Doctors [and] 2 Osgoods". This scene did indeed feature three incarnations of the Doctor, two Osgoods, as well as Clara and individuals resembling Kate Stewart and McGillop.