The TARDIS narrowly avoids becoming engulfed in a web-like substance in space. It then arrives in the London Underground railway system, the tunnels of which are being overrun by the web and by the Great Intelligence's robot Yeti. The time travellers learn that this crisis was precipitated when Professor Travers, whom they first met in the Himalayas some forty years earlier, accidentally caused one of the Yeti to be reactivated, opening the way for the Intelligence to make another invasion attempt. The travellers work alongside army forces - led initially by Captain Knight and then by Colonel Lethbridge-Stewart - as they battle against the alien menace, hampered by the fact that one of their number has fallen under the Intelligence's influence and is a traitor in their midst.
DVD Special Features: Presented in Black & White
Other Special Features: Subtitles: English SDH
Audio Tracks: Dolby Digital 2.0