The North Pole. 1983. A Russian submarine on routine Cold War exercises uncovers something frozen in the ice. Brought on board, the creature is discovered to be alive and soon escapes, attacking the crew and sending their vessel plummeting to the depths of the Arctic—just as a certain blue box materializes on their bridge—in Mark Gatiss's "Cold War."

"What is it? A mammoth?"

"It's not a mammoth." What it is is a "Martian reptile know as the Ice Warrior. When Mars turned cold, they had to adapt. They're biomechanoids—cyborgs," who "built themselves survival armor so they could exist in the freezing cold of their homeworld"—before that dying world finally scattered them all across the universe.

But this one's not just any Ice Warrior—that would be cause for pause enough—it's the Grand Marshal Skaldak, "the greatest hero that the proud Martian race has ever produced," frozen in the Arctic ice over 5,000 years ago.

Neither the Ice Warriors nor their Grand Marshal are strangers to the Doctor; he and they go way back (see the eponymous "The Ice Warriors," "The Seeds of Death," "The War Games," "The Mind of Evil," "The Curse of Peladon," and "The Monster of Peladon"). Fearing the worst, he quickly tries to broker a peace before either side—Ice Warrior or Russian—can declare war upon the other. But confined spaces and heightened emotions secondary to being trapped in a sunk/sinking submarine 700 meters below the polar ice cap don't mix well, and through a skittish scalawag's skullduggery—and with the help of a cattle prod—Skaldak is, shockingly, incapacitated.

"You idiot…! All we needed to do was let Skaldak go, and he'd have forgotten us. But you attacked him; you declared war. 'Harm one of us and you harm us all.' It's the ancient Martian code."

As the Grand Marshal regains consciousness, the Doctor sues for peace again—warily, through Clara this time—never suspecting that, desperate enough, an Ice Warrior would risk dishonor by fleeing his armor. But that's precisely what Skaldak, locked up, believing that he has been abandoned by his brothers, without a means of escape, and with nothing left to lose, has done.

"I never seen one do this before. Actually… I've never seen one out of its armor before…. It will be more dangerous."

It is. Xenomorph-like, Skaldak stalks the Firebird's crew—killing them one by one from the dark—

"It's in the walls!"

—until he reaches the nuclear submarine's launch control. There, having sonically summoning his armor, he prepares to launch a strike against the West—igniting a global nuclear war.

The Doctor intervenes with some sonic technology of his own: "I will blow this sub up before you can even reach that button Grand Marshal! Blow us all to oblivion!"

Skaldak is unmoved.

Clara tries. She begins singing "Hungry Like a Wolf."

The Ice Warrior relents, reminded of his daughter and the Songs of the Old Times—the Songs of the Red Snows—just as his brothers, having answered his call for aid, arrive.

Day saved.

Great Lines

Professor: "Have I interrupted something?"

Comrade Captain Zhukov: "We were about to blow up the world, Professor."

Professor Grisenko: "Again?"

Doctor: "What is that gas? Could be gas….! Ah. It never rains, but it pours."

Professor Grisenko: "We were drilling for oil in the ice. I though I found a mammoth."

Doctor: "It's not a mammoth!"

Doctor: "Five thousand years! That's a hell of a nap. Can't blame you for waking up on the wrong side of the bed."

Professor: "Correction: it's a big green man from Mars."

Professor: "I think that he wants to speak to the organ grinder, not to the monkey."

Clara: "I heard that!"

Doctor: "Oh! Professor, I could kiss you!"

Professor: "If you insist."

Clara: "Saved the world then?"

Doctor: "Yeah."

Clara: "That's what we do."

Wibbly-wobbly Timey-wimey… Stuff that You Might Have Missed

The episode takes place in 1983, approximately 2 years after Dave Oswald and Ellie Ravenwood met—possibly when their daughter, Clara, would have been a toddler (see "The Rings of Akhaten"). Perhaps not coincidentally, WarGames was released the same year: in addition to threatening its own version of Global Thermonuclear War, the film's title, at least in the context of "Cold War," might be considered a play upon the title of an earlier Ice Warrior appearance, "The War Games."

The Ice Warriors' last appearance was in 1974: in "The Monster of Peladon."

In myth, the phoenix, perhaps the most famous "fire bird," is reborn of its own ashes. The Doctor has regenerated 10 times since "An Unearthly Child"—twice since "Rose;" Clara has also died and been reborn at least twice—since "Asylum of the Daleks;" and other characters, notably, Capt. Jack Harkness, Jenny, the Master, Rory Williams, and River Song/Melody Pond have died (or been erased from existence) and come back—making rebirth a recurring theme, especially, in the new series.

When he is searched, the Doctor is found to have a Barbie doll, string, and his sonic screwdriver in his pockets.

The Doctor almost loses his sonic screwdriver for a third time in this episode.

Clara is able to understand and speak Russian in the episode—suggesting that the TARDIS may not dislike her as much as she thought (see "The Rings of Akhaten").

"Hungry Like a Wolf?" Wolves are no strangers to the new series—turning up as aliens in "Tooth and Claw." And then there were all those "Bad Wolves" in Series 1.

While, curiously, "breaking her in," the Doctor has reset the TARDIS's HADS—Hostile Action Displacement System.

Not seeing red? What about all those red stars? Red is the color of communism and was the indelible color of the Union of Soviet Socialist Republics, or "Soviet Union"—of which Russia was a part in 1983—until the USSR's collapse (and the effective end of the Cold War) in 1991. Red remains a prominent Russian color. The Ice Warriors hail from the Red Planet—as we learn from (or are reminded by) the Doctor while he's backlit by red emergency lights. The Doctor also uses the "red mode"  of his sonic screwdriver in his power struggle with Skaldak at the end of the episode. (For more on the "red mode," see "Silence in the Library.")

Speaking of which… when did the Doctor add the "red mode?" Did he add the "red mode?" The sonic was in the possession of the Professor, another doctor (no stranger to DOCTOR WHO, actor David Warner would make a passable First Doctor, don't you think?), for a good while.