Staff-Sergeant Arnold, who turns up dishevelled and bleeding, having somehow survived, links up with the Colonel and Jamie in the tunnels. All three agree to return to HQ to support the Doctor, though they find that he and Anne have left while searching for a Yeti to reprogram. At that moment, the fungus bursts through the walls of HQ, swamping Goodge Street shelter. Lethbridge-Stewart, Jamie, Arnold and Evans meet up with the Doctor and Anne, before the group is ambushed by the Yeti, who herd them to Piccadilly tube station. Arnold slips away and meets Chorley, who has been wandering the tube network and has become hysterical with fright.