Setting: Arctic circle, 30 miles west of GSO site
Time: Present era

A small skidoo races through the snow carrying a distressed rider. He wants to escape whatever he is racing away from.

One month earlier, the man - whose name tag identifies him as Chisholm - is chipping away at ice while a series of like-uniformed work around him. A supervisor or superior warns him to be careful as the site is ancient.

These memories from a month earlier seem to drive him madly onward. Chisholm is suddenly forced to stop his skidoo, dismount and search for some way around a giant wall of ice blocking his path. He keeps repeating to himself that he can't go back. He simply can't.

A month earlier, he recalls, he hit something incredible and began to unearth it.

In the present, Chisholm doesn't seem to be in control of himself as the memories overpower and disorient him. He falls backward into a crevice, screaming.

The object found was a Cyberman's arm.

In the TARDIS, the 11th Doctor - apparently still on his rock-and-roll obsession - plays noiseless air guitar and wraps up his story about failing to teach Elvis the G-sharp. Amy asks incredulously, "You taught Elvis to play guitar?" to which the Doctor responds, "Not very well, obviously ..."

Their light conversation is interrupted by an SOS signal that the TARDIS picks up. Amy asks if it was intended for the TARDIS but the Doctor doubts that. Distress beacons typically aren't choosy about who detects them. The TARDIS lands in the Arctic. The Doctor and Amy rush out in their normal, summery clothes - Doctor in his tweed jacket, classic dark bow tie and heeled shoes, Amy in her skirt, vest and heeled boots. Surprised, she asks where they are. The Doctor replies that it's just the Arctic and the TARDIS should keep them warm - at least for a while. Amy protests that they aren't wearing proper footwear for the arctic. As the Doctor distractedly notes that the distress signal wasn't very strong, the ground shakes beneath them.

Amy shouts "Earthquake" before correcting herself and shouting "er... Ice quake!" and reminds the Doctor about their heeled footwear.

The Doctor says they must be atop a floating ice plateau, and wants to go explore. "Didn't you listen to anything I just said?" shouts Amy. "No," states the Doctor and begins poking around the area. They have arrived just next to the abandoned skidoo. The Doctor takes the SatNav from it. Looking down into the crevice, a man's body can be seen and the Doctor decides to climb down. Amy waits as the Doctor jumps and climbs into the crevice - several feet deep. He searches the man's backpack for a medical aid and finds a metal container for water. Filling it from a nearby stream of melting ice and heating it with the sonic screwdriver, the Doctor produces a steaming mess caddie of water - "the perfect receptacle for water" as he opines - and regrets he hasn't any tea to make it more appetizing.

Reviving the delirious Chisholm, the Doctor learns that his ankle is injured and they decide to try to use the skidoo's cable to bring him up. However, when they attempt to do this, the entire skidoo comes crashing down upon them and they don't seem to have another means of getting back up to Amy and the TARDIS. Then, they notice the skidoo has destroyed a part of the ice wall and they are able to walk through it. Amy waits as the Doctor pushes enormous chunks of ice about the area to make a path for the weakened Chisholm to follow. When the Doctor climbs around a chasm that the new companion can't follow, the Doctor is forced to create a sort of ice bridge. He uses the sonic screwdriver to melt the base of an ice stalactite and pushes it across the ravine. It crashes down into place. Chisholm shuffles up the ice and they reach the TARDIS again.

The Doctor and Amy inquire immediately about the place Chisholm was running from. The archaeologist adamantly refuses to go anywhere near it, passing out from fright. Amy comments that Chisholm is delirious, but the Doctor corrects her - he's "terrified".

They bring him into the TARDIS and use the SatNav to look up the location of the GSO site. The TARDIS appears in the middle of the base, which is a lone refuge from the cold surrounded by a wire fence and miles of snow and ice in every direction. As they exit the TARDIS, Amy asks if the Doctor has ever seen the Thing. The Doctor asks whether she means "the John Carpenter, Kurt Russel Thing or the Howard Hawks thing-y with the walking carrot" and dismisses the question.

Chisholm attempts to stay calm enough to describe the attacks and what was happening to his friends when he initially fled earlier - namely, their transformation into robots. The Doctor seems to be picking up clues but suddenly a slithering metal leech-like robot leaps at Chisholm from behind and appears to "bite" him. Amy and the Doctor avoid the Cybermat and it is shooed away. Chisholm reacts in horror and flees to the base's tower to isolate himself.

The Doctor rubs his chin and wonders why a Cybermat would be programmed to infect people - turn them into robots - instead of kill them. They approach an airplane hangar-like building, which appears to be the main compound. However, when the Doctor knocks on the locked door, a menacing figure opens it. He has the head of a Cyberman hanging limply on his neck like a zombie. He sways, apparently ready to jump at the Doctor. "Who are you then?" asks the Doctor, as if innocently.

"Die," responds the man with the Cyberman head.

"Not much for conversation," says the Doctor, changing strategy. He shouts at Amy to figure out some way to disable the cyborg while he basically runs around in circles, just ahead of his pursuer. "Must eliminate ... Die ..." chants the cyborg. Amy thinks quickly and sneaks just behind the cyborg's circular path - which runs just past a steam vent. Clogging the outlet with the turn of a lever, she waits until the cyborg is just in range - then turns the lever to release the steam directly upon the cyborg. Electric bolts that resemble the deadly sign of a Cyberman attack run across the cyborg's body and it expires, screaming.

The Doctor breathes a heavy sigh and congratulates Amy on the quick thinking.

When they attempt to retrieve Chisholm from behind his locked door, he responds through the communicator that he would prefer them to save themselves. The Doctor promises that Chisholm will be spared and asks for more information about who to talk to about how to stop the Cybermen. Chisholm despondently replies that Elizabeth Meadows is the Senior Scientist and she should be inside the main compound. They leave him to wallow in the tower.

They take the pass key from the cyborg body and cautiously enter the locked door of the compound. This time, no cyborg greets them and they are able to sneak inside - finally out of the cold - and into the base. They deftly turn and avoid another person with a Cyberman head that is pacing just around the corner. The Doctor and Amy enter a room where a Cybermat is wagging its tail intimidatingly before a computer screen. The Doctor gives it a cyber-migraine with a specific burst of the sonic and it scurries through an air vent. The Doctor concludes that the clever awful things must have infested the airlocks of the entire base. If they can get to the entire nest and give it a giant cyber-migraine with an amplification of the sonic's signal, it might just disable the cyber-virus from spreading to whomever is left alive and hiding. Amy says those things are worse than spiders. The Doctor solemnly responds, "Spiders? I'd rather we change the subject" [displaying for the first time this particular Doctor's arachnophobia?]

On the computer, they discover that the project is a multi-national investigation - "a real brainy bunch" quips the Doctor - and Meadows' daughter would be turning 5 on May 5th - and the Doctor seems to think this is relatively soon. They also learn that Chisholm is the Chief Engineer and Archaeologist. They believe they can enter a locked chamber from the hallway using Meadows' daughter's birthday as a password. That seems to work - only too well! Meadows is inside this chamber and attacks the Doctor with an ice pick - then barely misses or avoids them as the Doctor dodges - wedging it firmly into a table.

They huddle inside the small makeshift lab, where a couple microscopes, files and a Cyberarm lay strewn on the tables. Meadows' arm is in a cast, which the Doctor eyes suspiciously but accepts as the 'injury' she explains it as. She tells them that she has been working privately in this room, thinking everyone else was dead or converted into Cyberslaves. She says she is trying to develop an antidote to the cyber virus. The Doctor immediately adopts this plan and offers to help her develop the cure to Cyberslavery. Meadows relates that this site - where they found the Cyberman arm - is 10,000 years old.

Amy and the Doctor get back to work trying to find a fresh sample of the cyborg blood. They locate the distress signal device, as it was sitting conveniently on a shelf in a nearby study, and use it to create their desired sonic screwdriver amp. They return to the computer room and examine the air vent. Amy suggests the Doctor climbs inside and - continuing his latest pop reference obsession - replies, "Am I wearing a Bruce Willis vest?"

Amy asks if he expects her to drop it right in the vent and the Doctor smiles. "You're a star!" he approves, "And you're even brighter than Alpha Ceti Beta 6."

As she climbs up into the vent-work, she narrates her experience (coming closer to the nest - seeing it - dropping the device in) but just as the signal activates, the vent-work gives way and she falls into a small radio room - where the wandering cyborg had stored himself! It immediately gives chase to her around a small table, repeating "Die ... Must eliminate ..." The Doctor pounds on the door, "Amy? Amy are you all right?!" In a matter of seconds, to avoid being distance-zapped by a cyborg bolt of electricity, Amy loosens some wires hanging from the ceiling, allows the cyborg to chase her round once more and flicks the light switch - completing the ceiling wiring's circuit with the cyborg's body. Electric shocks fly across the Cyberslave as it collapses. Amy has killed another cyborg and saved her own life.

The Doctor gets through the door and Amy is able to meet with him about the radio in the room. All at once, the radio is active. It calls, "Fort Cecil to GSO Zebra Bay! We are coming in for a delivery ..." The Doctor tries to communicate back to warn them, but they don't respond. Amy realizes the signals can be received but not sent. The Doctor quickly locates the problem. Amy is assigned to replace the capacitor and warn them not to come near to prevent more bodies to be used by the cyber virus. He removes the nano-synthesizer from the dead Cyberslave and dashes off to try to come up with a cure for the virus. Unsure of where to find a capacitor, Amy goes back outside into the cold to Chisholm's tower communicator. She asks if he is alright and if he knows where there is a replacement capacitor. He sounds worse than before but is able to tell her the combination to a locker which stores a replacement.

After repairing the radio, she warns the Fort Cecil signal not to come any closer because of an outbreak of "polar flu" that must be quarantined. They reply that they understand and will be by later - "Over and Out."

Amy asks herself, "They actually say that?"

The Doctor has created a cure using Meadows' small lab, but Meadows herself was nowhere to be found when he got there. Perturbed by the disappearance of Meadows but unflappable a team as ever, the Doctor and Amy rush to Chishom with the cure. He reluctantly emerges from behind the giant metal door and reveals himself. His right arm has completely transformed into a Cyberman arm and his face is horrifyingly halfway between his human face and that of a Cyberslave. The Doctor and Amy get him inside the compound and into the lab where he can safely heal from the nanotechnology. They, however, must go on as he lays on the lab floor.

They activate the lift inside the makeshift lab - which is actually a lift hallway - and descend several levels into the ice. When they come out, they encounter a vast, layered network of criss-crossing tunnels - filled with pacing, searching Cyberslaves. Apparently, someone has been alerted of their presence because the Cyberslaves are looking for intruders. They quickly dodge around Cyberslave after Cyberslave, into nooks and hallways and climb down ladders until they must be much deeper into the ice than before. As they round a corner, they discover the tunnel they are in connects to an enormous cavern. A Cyberman ship is embedded in the ice and covered with a lattice of catwalks. The ceiling appears to be over 100 feet above them, the cavern well lit from inside by flood lights and light from the ship itself.

Amy gawks and asks if this ship has really been here for 10,000 years. The Doctor responds that it has been hibernating, waiting for explorers to send out the Cybermats and create Cyberslaves - using minimal energy to awaken an army of Cybermen that will convert all of human life into Cybermen. [It is worth noting at this point that the Doctor "remembers" through a bonus "WHO FACT" during earlier gameplay that Cybermen are originally from Earth's twin planet Mondas, which goes some way to explaining why the Cybermen are so compatible with Earth humans.]

Amy and the Doctor attempt to climb up to the helm of the spaceship using the catwalks, but they find to their chagrin that they can only ascend using pneumatic lifts that require one person going up at a time - because someone has to remain on the previous level to activate the switches. After staggering their ascent in turns, and making slow progress upwards, the Doctor asks Amy to go up before him on the third lift. When she reaches the top of the lift, two Cyberslaves escort her away. "Amy!" yells the Doctor, but he knows it's too late. He must figure out where she is being taken. He whips out the sonic screwdriver and risks it on a few disabled lifts to reach the top quickly, and dashes through the doorway to the bridge of the craft.

Inside, a dramatic scene is presented for the Doctor. Elizabeth Meadows, her 'injured' arm revealed as a Cyberman arm, her eyes being encroached by gray, cybernetic veins, defies the Doctor with an image of Amy in a Cyberman conversion chair. The Doctor begins to make demands but Meadows explains everything; they crashed a long time ago in the Arctic. Now the Doctor has a choice - to awaken the Cyberman army immediately or his friend dies. The Doctor, now well experienced in these specific negotiations, accepts the terms immediately - he will release the Cyberman army in exchange for Amy's life, but not before adding that he now knows Meadows was a Cyberslave all along. The Doctor completes the program using the ship's computer and the awakening begins.

Cyberslave Meadows ignores the Doctor as she brings the Cyberman leader to life with a switch. The official Cyberman leader, with a black casing around a transparent window to what was once a human brain, does indeed awaken. "Lord, I have reactivated you," declares Cyberslave Meadows in fright. The Doctor recognizes what's happening and shouts to the Cyberleader, "No, you don't have to kill her!" but it's too late. Speaking as quickly as it was revived, the Cyberleader emits that they have no need for Cyberslaves, "Cybermen are superior to all," and blasts Meadows dead. Switching quickly into Doctor-delete mode, the Cyberleader fires at the Doctor as he runs out of the room and into the ship's halls.

He quickly navigates around awakened Cybermen into the Cyberman conversion chamber and locks the door's opening mechanism. The Cybermen begin ramming on the door with their fists and it's only a matter of time before their door fails and the Cybermen are upon Amy and the Doctor. He releases the manacles of the chair and Amy leaps out, ready for action. However, they must find another way out because there are far too many Cybermen behind the door the Doctor just entered from.

Using switches to aim the chair's conversion beams toward the back of the frozen room, the Doctor uses the conversion chair's own weaponry to blast a hole in the ice. Amy and the Doctor escape the room through the hole and round the back of the ship's bridge. But before they can leave the base entirely, the Doctor must undo the awakening before the Cyberman army takes over Earth. They enter the bridge and find it abandoned enough for the Doctor to access the ship's computer.

He intends to use the discoveries he made creating the Cyberslave antidote to reverse the Cyberman awakening. He believes that by making the ship's program reverse itself, he can force the blood of all the Cybermen to reverse the nanosynthesis process and remotely destroy all the Cybermen on Earth. The Cyber leader appears to put a stop to them, announcing that they are to be deleted. Things appear grim, when a fully recovered and fully human Chisholm appears just as suddenly to take out the Cyber leader with some electrical weaponry of his own - the originally discovered Cyberarm!

The Doctor seems impressed to see his virus-cure work - and Chisholm both alive and human. Chisholm declares just how happy he really is and begins kicking the metal of the collapsed Cyber leader.

The Doctor doesn't want to take any chances on the cyber base becoming active and has programmed the ship to self-destruct. Unfortunately, Amy, Chisholm and the Doctor have less than a minute by now to escape. They run down the catwalks, down a pneumatic lift, across a pneumatic bridge, out of the enormous chamber, into the tunnel network and up a lift. As they race out into the cold, the GSO base rocks and explodes from underneath - knocking the trio into the snow.

As they get up, finally feeling somewhat safe from the cyber threat, the Doctor remarks that it all went according to plan ... "in the end."

Amy skeptically asks, "Do you even know what a plan ... is?"

The sound of the engines of a small plane overhead indicates the presence of the Fort Cecil delivery crew. Chisholm has a way home and the Doctor and Amy find it's a fine time to depart. There is one thing that UNIT never got used to about his name, remarks the Doctor cryptically to Chisholm. Chisholm asks who he is. The Doctor replies, "The Doctor. Just the Doctor." Amy and the Doctor step into the TARDIS and depart.