When their HQ is destroyed by the web and everyone is captured by Yetis, all seems lost.
The Great Intelligence demands that the Doctor allows his mind to be drained.
The Doctor is able to acquire a sample of the web but the Yeti strike back at Travers.
The Doctor meets Colonel Lethbridge-Stewart who takes control of the military operation.
The deadly web continues to advance in the tunnels of the Underground.
The TARDIS lands in the London Underground, which is deserted apart from a glowing web.