They open fire on the Yeti, but bullets appear to have no effect on the robotic monsters. The Yeti carry guns and one of them fires at a soldier, smothering him in web fungus. Another fires at the TNT, covering them as well.
Karl secures a gun for himself and tries to rescue the soldier who has been covered in the fungus, but soon realises he can’t as the Yeti close in threateningly.
They are forced to retreat back into Moorgate station. Although the links to the surface are blocked, they are able to pass through to other platforms. Lang takes them to the Metropolitan line, leading them towards Kings Cross St Pancras. The Yeti are in pursuit, but they are slow and can be out-run.
In the tunnel they leave the Yeti behind. Karl and Corporal Lang mention hearing a faint beeping noise intermittently, but they cannot trace the source. Frederick mentions he heard it in Tibet as the noise of a stray sphere looking for a Yeti.
They proceed on towards Kings Cross St Pancras. Lang mentions that Kings Cross St Pancras is blocked by fungus on the Northern line, hopefully the Metropolitan Line is clear.
Frederick asks what the cover story is for the population above. Lang says London is evacuated and there is fog that kills people. It’s a national emergency.
The Metropolitan line is clear at Kings Cross and they make their way to the Piccadilly line to head towards Holborn. They hear gun shots, shouting and Yeti roars ahead and pause, but Corporal Lang wants to catch up and find out what is going on.
At they arrive at Holborn, there is no sign of any soldiers, but they can still hear gun shots, apparently coming from the station above them. A Yeti suddenly emerges out of the shadows and attacks Lang, killing him in a single blow.
Frederick activates his sonic screwdriver. It is set to the same frequency as the Yeti transmissions and the creature pauses then lumbers off.
While examining Lang’s body, they find a small toy sized Yeti – one of the figures that was originally on the board in front of the Master’s throne in Tibet. It must have attracted the Yeti. Frederick de-activates it.
Then a figure emerges out of the shadows, some sort of officer in Scottish uniform, pointing his revolver and demanding to know who they are. They introduce themselves, but he wants their ID. Thaddius shows him the psychic paper but after a pause and a frown, he says it’s blank. Thaddius uses telepathic suggestion to make him believe the ID is genuine.
The officer has them head to the HQ at Goodge Street, though he remains behind them, pointing his gun at them at all times. When they arrive, he introduces himself to Captain Knight as Colonel Lethbridge-Stewart, the new commanding officer and shows him his papers. He came in with the ammunition truck delivery to Holborn, but when they arrived, the trucks were attacked by Yeti and everyone was either killed or scattered.
Colonel Lethbridge-Stewart then calls a meeting of everyone to discuss the situation and what they can do. Everyone is there, including Professor and Anne Travers, Chorley, Captain Knight, the Time Travellers, Karl and all the soldiers.
During the meeting, they bring the Colonel up to date with events and how the Yeti seem to be able anticipate their moves. Lethbridge-Steward order an armed party to go to Holborn and recover the ammunition. Captain Knight leads Sergeant Osgood and most of the soldiers out on this mission.
The civilians, Chorley, Anne, Professor Travers and Frederick go to the lab to continue to search for a solution to their problems. Frederick starts working on modifying a Yeti sphere to transmit a jamming signal, to block commands reaching the Yeti and perhaps causing them to do nothing without orders. He recalls that Yeti in Tibet could stand idle and ignore you if they had no orders.
Colonel Lethbridge-Stewart, Thaddius, Karl, Corporal Blake and Private Weems stay behind to protect the HQ.
A while later, Private Weems, who is on watch, runs back into HQ saying four Yeti are approaching. The soldiers quickly prepare for attack, but when the Yeti burst through the door, bullets do not stop them.
Thaddius warns the civilians and scientists in the lab. They hastily gather what equipment they can and head into the control room, but the Yeti are between them and the exit. The Yeti continue to advance, killing Corporal Blake.
Two of the Yeti close in on and seize Professor Travers, dragging him away while the other two bar the way. The two remaining Yeti then begin advancing towards the rest of the cornered survivors menacingly and a desperate battle ensues. The journalist Chorley is able to slip past them and escape, by pushing Thaddius towards one of the other Yeti.
Frederick decides to try his new jamming sphere on the two remaining Yeti and discovers it works, but only at a range of two feet! As the Yeti are standing next to each other, he is able to disable them both. He takes the spheres out of the chests of both the Yeti and the scientists take them to the lab to create more jamming spheres. Knowing the spheres can move of their own accord, he keeps them next to the jamming sphere so they do not become active.
Ann is distraught at the Yeti taking her father. They check outside, but there is no sign of him or the Yeti who took him. Ann resolves to continue his work to stop them.
Colonel Lethbridge-Stewart is concerned that Captain Knight has not returned and decides to head there himself. With no soldiers left, he gathers Thaddius and a reluctant Karl to go with him to Holborn to see what has happened to Captain Knight.
On the way they encounter Private Evans, a nervous Welsh driver, who says he ran when the Yeti attacked. Lethbridge-Stewart has him join their party.
When they reach Holborn, they head for the surface, where the gates are open. They find the ammunition trucks that the Colonel came in on. There are many dead soldiers lying around in the mist. Evans panics and runs off.
They find Captain Knight and some of his party dead. Knight has been shot in the back, probably with his own pistol which is missing. Thaddius speculates that the journalist, Chorley, did not have a gun of his own, wondering if he is the traitor. There is no sign of Sergeant Osgood, so he may have survived.
The trucks are still loaded with ammunition, so they take grenades and TNT back down to the Underground. When they reach the platform, they find the fungus is advancing towards Holborn, led by a Yeti carrying a glowing pyramid. They use TNT to blow up the Yeti and the fungus advance stops.
They decide to return to HQ at Goodge St. There they find Frederick is working on a transmitter that will not just jam the Yeti – he hopes to give them orders of his own. He brings it from the lab to the main control room to show the Colonel.
Suddenly four more Yeti enter the unguarded door, carrying web guns. With them is a white-faced Professor Travers. To Ann’s distress, he speaks, but with the cold, evil voice of the Great Intelligence.
He tells them their pathetic efforts to stop him will not succeed. One of the Yeti uses its web fun to destroy Frederick’s transmitter. He then says he has come to take the Time Travellers, Frederick and Thaddius.