Arnold and Lane put on gas masks and attempt to go through the fungus blocking Covent Garden with the baggage trolley, but when they enter the web Evans hears piercing screams. On pulling the trolley out on a rope, Evans finds Lane dead and Arnold gone. On the surface, the Yeti ambush the soldiers at Covent Garden. Despite downing several robots in the ensuing battle, all except Lethbridge-Stewart perish. At an electronics store on the surface, Knight is killed in a Yeti attack, though the robots leave the Doctor alone. He discovers a Yeti beacon in Knight's pocket, which brought them to the shop. Later, the Colonel returns to HQ alone where the Doctor finds a model Yeti in his pocket. The Doctor deduces that the traitor in HQ slipped the beacon onto the Colonel and Knight. At that moment, two Yeti break in with Professor Travers, who is possessed by the Great Intelligence.