Moving through the underground train tunnels, the Doctor and his companions encounter the military, who are trying to stem the spread of the fungus by demolishing tunnels with explosives. Explosives laid at Charing Cross tube station are neutralised by the robot Yeti by smothering the explosion with the fungus using web-spraying guns. The reappearance of the Yeti signifies to the Doctor that the Great Intelligence has returned and redirected the TARDIS' flight in order to bring him to the Underground as part of its plans to conquer the Earth. Knight, Arnold and Chorley are initially suspicious of the Doctor, Jamie and Victoria, believing them to be responsible for sabotaging the explosion. Professor Travers, recognising them from their encounter in Tibet, convinces Knight that the Doctor will be key to defeating the Yeti.