They chained up Skaldak in a dank corner of the submarine, while the Doctor gave everyone a quick tutorial in Ice Warrior history. They're a race of Martian reptiles who transformed themselves into bio-mechanoid cyborgs so they could exist in the cold; a sudden increase in temperature makes them go haywire, which is why the Cattle Prod attack worked on him. If they had just let Skaldak go, they would have all been safe. But that was before the attack by the Lieutenant. (Played by Tobias Menzies -- who, coincidentally, is also from Game of Thrones, since he'll pop up this year as Edmure Tully. Scientists estimate that the entire population of the British Isles will be cast on Game of Thrones by 2018.) Ancient Martian Code does not abide attacks -- the lives of everyone onboard the submarine were forfeit.
Immediately, the double meaning of this episode's title became clear: We were watching a story set in the Cold War, but we were also watching an allegorical exploration of the Cold War, with two sides who only wanted to defend themselves leading each other into an apocalyptic game of brinksmanship. (In the makeshift brig, Skaldak set off a distress beacon: "Find me, my brothers, if you are still out there.")
Clara is still learning the ropes of this whole time-space-adventure thing -- the Doctor had to explain to her that she was currently speaking Russian, thanks to the TARDIS' translation matrix. But she happily volunteered for a dangerous duty. The Doctor wouldn't let the Russians speak to Skaldak; he would smell the Soldier on them. The same applied to the Doctor, of course. "I don't smell of anything," said Clara, "To my knowlege." A look flashed across the Doctor's face. A look that said, "Actually, Clara, you smell like 'curious temporal phenomenon that has somehow created the same single human being in three different time periods, if not more.'"
But soon she was walking to Skaldak's lair, flashing the Ice Warrior fist-over-the-heart salute. She parroted the Doctor's delicate diplomatic overture: "This isn't what you deserve. You are not our enemy." Lurking in the shadows, Skaldak rhapsodized about his final moments pre-permafrost. Fighting side-by-side with his daughter. "We sang the songs of old times, the songs of the red snow." Five thousand years had passed, he knew: "My daughter will be dust." He sounded like a man/reptile with nothing left to lose. And worse, he was loose: The armor was empty. Clara fled to the door; when the Doctor opened it, a shape quickly moved past her and the crewmen outside. "I've never seen one outside of its armor before," said the Doctor. Wouldn't that make it more vulnerable? "No," he said darkly, "It'll be more dangerous."
Elsewhere in the submarine, Lieutenant Brutus was inspecting the shadows when the shadows started inspecting him. Long reptile fingers encircled his skull. The Lieutenant made a pitch to his Martian assailant. "We can form an alliance to win the Cold War." He gave Skaldak a quick rundown of the history of Mutually Assured Destruction, which made the space-lizard positively purr with pleasure. Exit Brutus.
Meanwhile, the Doctor was giving Clara a quick lesson in time travel rules. "The world didn't end in 1983," Clara protested, noting that there was no way an Ice Warrior could have ignited a global conflagration just two years after the Most Important Leaf in the World inadvertently led to Clara's creation. "History is in flux," the Doctor explained. "It can be changed. Rewritten." This is a defining tenet of the Steven Moffat Doctor Who era; it's a conception of time that sees time as a geographical map, with different time periods reimagined as states with hazy borders who occasionally attack each other. Ambient Theorizing: If time can be "rewritten," can it also be plagiarized? Will that somehow factor into the Mystery of Clara, an apparently unique individual who exists un-uniquely across space and time? Could there be a "Clara" in each time period? Are they multiplying? Will everyone across space and time become Clara Oswin Oswald? And is that a problem the Doctor will have to "solve"?
NEXT: Skaldak goes all Alien on the Soviets