The Great Intelligence speaking through Professor Travers tells the two Time Travellers, Thaddius and Frederick, he wants them to surrender to him willingly or everyone else here will be killed. They have one hour to decide. He then departs.
As he leaves Frederick, Thaddius and Karl notice everyone else slow down and stop, like time has stopped. Then a space suited figure begins to materialise at the end of the room. The others assume a defensive posture, raising their guns. The figure points to Karl and gestures for him to come over.
Karl does so and the figure turns its back on the others and takes its helmet off, so that only Karl can see who it is. Karl seems surprised, then seems to relax and lower his weapon. Unknown to the others the figure is actually Karl himself from the future.
The figure mutters a few words to him and Karl puts on the Time Bracelet that Frederick gave him. At the end the figure says more loudly “Don’t let them kill ...” but fades away before he can complete the sentence.
Time then seems to flow again and the surprised Time Travellers turn back their attention to the others in the room. Col. Lethbridge-Stewart demands to know what is going on and what this talk of time travel is. Frederick explains what he can to him, but is not able to say they are Time Agents.
They discuss what to do next. The transmitter has been destroyed. They will need another one if they are going to stop the Intelligence. Col. Lethbridge-Stewart recalls that there was an electrical shop above Holborn station where the ammunition truck was ambushed.
They still have the Yeti jamming spheres and a box of grenades. Everyone is given a grenade except for Anne Travers and they head off for Holborn, leaving the HQ abandoned. They find two Yeti guarding the exit to Goodge Street but deal with them using grenades, which are powerful enough to break the Yeti outer casing and damage then significantly, disabling them.
When they arrive at Tottenham Court Road, they find four Yeti guarding the platform, two of which are armed with web guns. Karl distracts them by running past, but one of them chases after him while the Colonel and Thaddius deal with the rest. A combination of grenades and a good head shot disables the Yeti chasing Karl and they all survive.
They proceed to Holborn, where they find the web fungus but it is beginning to break through the walls. They head up to the surface, to find the fog has closed in thickly. It is deadly at this concentration, so they will have to use gas masks. Frederick turns pale and refuses, he seems terrified of the idea.
They are forced to leave him behind with Private Weems to look after him while the Colonel, Thaddius, Karl and Anne head into the fog, looking for the electrical shop. After a quick search they find the place and begin to look around for the equipment they would need.
Thaddius catches a glimpse of a figure in the fog outside the shop and fires, but the figure seems to survive and return fire with some sort of laser gun, stunning Thaddius to the floor, though he is still conscious. The figure then rolls a stun grenade into the shop and it goes off, knocking out Thaddius and the Colonel. Karl is stunned and retreats behind the counter. Anne is not effected at the back of the shop.
The figure is wearing some sort of advanced breathing mask, but from his clothes it looks like the journalist Chorley. He tells Karl from the doorway that he is disappointed he put on the Time Bracelet. The people he is working for are trying to change the future to stop the Daleks.
The victory of the Great Intelligence now will save the Humans from the virus that caused the Zombie outbreak that Karl fled from. He is here to kill the one who will stop the Great Intelligence – Colonel Lethbridge-Stewart. Chorley then shoots at the unconscious Colonel. Karl shoots Chorley multiple times, badly injuring him and a slightly different Time Bracelet on his wrist beeps and he vanishes into time.
Karl checks the Colonel and his arm and shoulder are badly wounded, but he is alive. He needs help to move him so he leaves Anne to tend to him and runs back to get Frederick and Weems. Frederick refuses to help as he cannot put on a gas mask, so Weems goes with him, taking what he can to form a makeshift stretcher.
They carry the Colonel out. They collect Frederick in the station and grab what first aid treatment they can find. They then head towards Goodge Street, but find the platform at Holborn flooded with web fungus. They are forced to try an alternative route, taking the Piccadilly line to Leicester Square and then catching the Northern line to Tottenham Court Road and Goodge Street.
It is a frustrating journey, having to transport the Colonel on his stretcher, while keeping an eye out for Yeti. When they reach Goodge Street, they find HQ has been flooded with the web fungus. They are forced to use a station side room to work on the transmitter until Frederick thinks it is ready.
The fungus continues to advance towards their new workshop though and they are have to move on. They decide to follow the Northern line, heading to Euston, which may still be open. On the track along the way, they find the unconscious body of Sergeant Osgood, who has marks from Yeti attack and seems rather confused.
He tells them in his northern tones that the mission to the ammunition truck was ambushed and they were all forced to scatter and hide. He has some morphine he is able to give the Colonel to help him get up and walk. They head towards Warren Street, with the Sergeant taking charge of the grenade box.
When they get to Warren Street, Sgt Osgood suddenly cocks his rifle and steps back, telling everyone to stand still. Four Yeti emerge from the platform exits and Osgood’s voice changes to that of the Great Intelligence, telling them to surrender. He then orders the Yeti to seize them.
Anne uses her Yeti jamming sphere to stop the Yeti trying to get her. Frederick, Thaddius and the Colonel are grabbed. Karl confronts the possessed Osgood, who points his gun at Karl’s head and tells him to lower his gun, which he does.
Frederick uses his sonic screwdriver to open the flap on the Yeti he has been seized by and takes out the control sphere. It stops but the sphere tries to go back to the robot. He uses the screwdriver to open the sphere and disable it.
Thaddius uses his psi ability to mentally attack the possessed Osgood, who is stunned momentarily. Frederick goes over to Anne to get the other jamming sphere and the transmitter, looking for somewhere to plug it in.
The possessed Osgood draws on the mental powers of the Great Intelligence and attacks Thaddius, knocking him out with a powerful attack. Karl takes the opportunity to shoot Osgood but realises that the body is dead – he’s some sort of zombie!
Osgood calls in Yeti reinforcements as Karl fires a full burst at him, hitting him in the head. He collapses and his body appeared to be inanimate, but glowing web fungus oozes out of the body and begins to head towards the next nearest body, the unconscious Thaddius.
Anne uses one jamming sphere to hold off two Yeti while Karl uses grenades to keep other approaching Yeti back. Frederick is able to plug the transmitter into a nearby power line and after some adjustment turns the power up to maximum on the frequency the Intelligence is using.
All the Yeti suddenly stop and the fungus makes some sort of high-pitched scream. After a few minutes of sustained transmission, the fungus stops screaming and goes dormant, losing its glow. Col. Lethbridge-Stewart comments that a military intelligence division needs to be set up to combat this sort of alien menace.
Shortly afterwards the Time Bracelets of the three Time Travellers go off and they vanish into time.