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Recap / Doctor Who S33 E4 "The Power of Three"

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"Every time we flew away with the Doctor, we'd just become part of his life, but he never stood still long enough to become part of ours. Except once..."
Amy Pond

The year of a ton of cubes, the first one with the Brig's daughternote , and the one where the Doctor plays Wii Sports and gets very bored.

AKA: The Year of the Slow Invasion.

Written by Chris Chibnall.

One day, approximately ten years after Amy and Rory started travelling with the Doctor (in their relative time), billions of tiny black cubes fall out of the sky. Professor Brian Cox is on TV talking about it and everything. The Doctor and his Ponds — including Rory's dad Brian — investigate, with the help of UNIT's new scientific leader, Kate Stewart. The Doctor decides to stay with Amy and Rory for a while and gets to know them as they do their everyday jobs and live their everyday lives. Amy is now a travel journalist and Rory is considering nursing full-time.

Only the cubes don't do anything. The Doctor can't bear the endless waiting, and takes Amy and Rory on more and more adventures just to stave off the boredom. They fight Zygons, end up in Henry VIII's bedroom, and so on. Months pass, then a year. Meanwhile, Brian is getting increasingly worried about his son and daughter-in-law when he figures out what kinds of things usually happen to the Doctor's companions in the end. The Doctor decides to shelve his rampant Attention Deficit... Ooh, Shiny! for a while and comes to properly live with the Ponds, because he just misses them terribly when they're not around. Brian keeps a daily video log of the cubes, but all they do is sit and be utterly, completely indestructible.

When the cubes eventually start moving, they light up, spit out fire, experiment on humanity and play "The Birdie Song". The Doctor rushes over to UNIT with Amy in tow, while Rory and Brian discover a starship portal in Rory's hospital and some rather scary aliens. While the Doctor and Amy have a quiet Friendship Moment, realising that their adventures can't last forever, the cubes start a global countdown after which they directly attack people's hearts, sending a third of Earth's population into cardiac arrest. Fortunately, the Doctor has more than one heart, and has both of them restored to full health after Chewing the Scenery for a bit. Even more fortunately, Kate Stewart turns out to be Kate Lethbridge-Stewart, the daughter of The Brigadier, and the Doctor knows he can trust her completely.

The Doctor and Amy rush over to the starship portal and confront the Monster of the Week: the Shakri, a bogeyman from Gallifreyan bedtime stories who wants to kill humanity with the cubes as a kind of interstellar pest control. The Doctor saves humanity when he realises he can Reverse the Polarity on the cubes. Then Kate gives the Doctor a kiss on the cheek, and Brian gives Amy and Rory his blessing to travel with the Doctor a while longer.


  • 20 Minutes into the Future: Amy and Rory have been married for ten years (in their personal timeline). When the story is set is unclear, as she's adding Earth time and Doctor time together. And then the episode follows them for a year in real time. Fans have done the math of the two year Time Skip between Series 6 and 7a, and conclude the Slow Invasion occurred between 2014 and 2015, but then the Doctor meets Kate in a 2013 adventure during the 50th, despite them meeting for the first time in this episode. It gets very wibbly-wobbly.
  • Accidental Marriage: Amy accidentally marries Henry VIII. This is both a Call-Back and a Call-Forward: It makes Amy Elizabeth I's stepmother; thus, it makes her the Doctor's step-mother-in-law and mother-in-law. It also explains how Rory left his cell phone charger in Henry's court. It also makes Henry VIII the Doctor's father-in-law and step-father-in-law as well through his tenth and eleven incarnations.
  • Alien Invasion: The slow invasion by lots of little black cubes falling from the sky all around the world. They want to kill all humans.
  • Allergic to Routine: The Doctor still really hates waiting. He counted bouncing a football five million times and was annoyed to be informed only an hour had passed. He also vacuumed the house, painted the fence, and mowed the lawn in between bouncing the football.
  • All Myths Are True: The Shakri are a Gallifreyan myth, yet they are also responsible for the slow invasion.
  • Armor-Piercing Question: The Doctor is taken aback when Brian asks what happened to the other people who traveled with him.
  • Arson, Murder, and Jaywalking: The cubes can, among other things, stop people's hearts, fire lasers... and play "The Birdie Song". The Doctor and Amy do not approve.
  • Artistic Licence Medicine:
    • Rory, who is a nurse, says that "mass defibrillation" is needed to restart all the stopped hearts, but defibrillators don't work like that. They restore normal rhythm in hearts in ventricular tachycardia or fibrillation (hence the name).
    • For that reason, you can't restart a person's heart with a defibrillator, as Amy does for the Doctor with one of his two hearts. Maybe justified given the Doctor's Bizarre Alien Biology, but it's a big maybe.
    • Restart someone's heart after a period of death and no oxygen to the brain? They at least had the decency to have the newsreaders say that emergency care was being set up for those affected, implying they weren't immediately back to full health, but the people shown coming back still seemed to be doing remarkably well to say they'd just been dead.
  • As Himself: Professor Brian Cox and Lord Alan Sugar make cameos as themselves.
  • Badass Boast: The Doctor gives one to a cube... while playing Wii Sports.
    The Doctor: This planet, these people are precious to me. And I will defend them until my last breath.
  • Big Bad: The Shakri.
  • Body Horror: There are two fake "nurses" who abduct humans from the hospital and take them to the Shakri ship, and they wear surgical masks to hide that they don't have mouths. Instead, they have something that looks like a vent.
  • Breather Episode: One last fun outing with the Ponds before things get sad next episode.
  • The Bus Came Back: UNIT returns for the first time in the Steven Moffat era.
  • Call-Back: The Doctor talks about a couple previous events and characters.
    • What's happened to some of his previous Companions: those who have left, those who have been left behind and those who have died.
    • Kate Stewart learned the philosophy of "science leads" from her father, who in turn got it from his old friend.
    • He mentions he used to have a metal dog that could float.
    • The Doctor's inability to handle the boredom of living in normal time on Earth echoes his third incarnation's irritation at being stuck on Earth for much of his career, and this is only reinforced by his cooperation with UNIT and the presence of a Lethbridge-Stewart.
    • Particularly astute viewers might pick up on the Doctor's quite justified fear of defibrillators.
  • Canon Immigrant: Kate Stewart made various appearances in spin-off media before appearing in the show. Her previous onscreen adventures were a straight-to-video release with companions Sarah Jane Smith and Victoria Waterfield called Downtime, and its sequel Demos Rising which focused on her and another Downtime character, Douglas Cavendish.
  • Companion Cube: After a montage showing people using the cubes to play golf and to make espresso, cut to a little girl in a hospital holding her cube like a dolly.
  • Continuity Nod: Quite a few background references are present in the episode as well.
  • Couch Gag: The show's title is a tessellated pattern of cubes.
  • Creepy Child: The little girl... droid... thing. She just sits there staring into space and stroking the cube while it glows and the light reflects in her eyes.
  • Creepy Twins: The two cube orderlies who keep kidnapping people.
  • Cuddle Bug: The Doctor spends a lot of time in this episode kissing Amy's forehead and cuddling her, because he knows she's considering a life without him. Rory even gets in on it, grabbing the Doctor's face and snogging him as a thanks for their wedding anniversary gift.
  • Deadpan Snarker: Kate has her moments, such as when she claims her team is trained in beheadings and she has ravens of death. It's appropriate, considering her lineage.
  • Description Cut: The news reports show Professor Brian Cox saying that "the answer must come from a greater man than I." Cut to the Doctor looking at a cube.
  • Determinator:
    • Brian keeps diligently watching the cubes long after the world stops caring, all because the Doctor asked him too.
    • The Doctor counts, after one of his hearts stops. Time Lords are not meant to go about with just one.
  • Diabolus ex Nihilo: Although it's obvious someone's behind the cubes, there are no hints as to the identity or motive of this Monster of the Week until the last few minutes of the show.
  • Doomed New Clothes: Amy's Pimped-Out Dress gets a bit charred, as does Rory's new tux.
  • Double-Meaning Title: The title refers both to the invasion of cubes and the Doctor, Amy and Rory being the resident Power Trio.
  • Dumb Muscle: Kate Stewart seems to regard the UNIT troops and possibly the older, not so Mildly Military, commanders as this. In her first scene, she says they don't know how to knock on a door, only storm the place, and that she had to drag them "kicking and screaming" into a science direction.
  • Elaborate Underground Base: UNIT has one underneath the Tower of London, and it's a big one with all kinds of alien junk stored away. This episode features a testing facility of the cubes. It also has trained beheaders and ravens of death.
  • Emotion Bomb: One of the cubes can inflict mood swings.
  • "Eureka!" Moment: "Oh, Amelia Pond... "you always get what you want"... [the cubes] got what they wanted."
  • Faux Horrific: One of the cubes emits the Birdie Song/Chicken Dance on a constant loop. The Doctor and Amy are suitably horrified.
  • Foreshadowing: At the very start of the episode, you can hear a voice message saying how a pair of reading glasses were ready to be picked up. Guess what Amy is wearing in the next episode?
  • Gilligan Cut: The Doctor drops Amy and Rory off at the Savoy in 1890 for their wedding anniversary, promising "no surprises". Cut to them sitting in a burned out hotel:
    The Doctor: Bit of a shock. Zygon ship under the Savoy. Half the staff impostors.
  • Historical In-Joke: The Doctor claims to have invented the Yorkshire pudding.
    The Doctor: Sweet, yet savoury. [holds up a custard-dipped fish finger] Sound familiar?
  • Hoist by His Own Petard: The Doctor foils the Shakri's scheme by hacking into the control hub they were using to manipulate their cubes, and simply reversed the polarity to force said cubes to undo the damage they caused.
  • Humans Are the Real Monsters: This is the motivation for why the cubes are used, to prevent the spread of humanity throughout space because they are a plague.
  • Humans Are Special: The Doctor counters the trope above, with the Picard Speech, however; claiming that while Humans may make mistakes (like any species can), they learn from them and work to better themselves, with their achievements outweighing anything negative about them, and the Doctor is always on their side.
  • I Always Wanted to Say That:
    Rory: There are soldiers all over my house, and I'm in my pants!
    Amy: My whole life I've dreamed of saying that, and I miss it by being someone else.
  • Ill-Timed Sneeze: Rory, the Doctor and Amy are hiding under Henry VIII's bed. The Doctor sneezes.
  • Internal Homage: A homage to Russell T Davies-era Earth-invasion stories, with a dash of the Jon Pertwee "exiled to Earth" Myth Arc thrown in.
  • It Came from the Fridge: Amy is cleaning out the fridge; there is milk two months out of date, and when she picks up the yogurt, she simply screams and throws it.
  • Large Ham: Matt Smith gives his grand ode to overacting after one of the Doctor's hearts stops, and it's glorious!
  • Like Father, Like Son:
    • Brian is a Determinator who calls the Doctor out. He truly is Rory's dad.
    • Kate seems a lot like her dad, the Brigadier; leader of UNIT, snarky British lady, and heroic defender of Earth.
  • Made of Indestructium: Kate has subjected the cubes to positive and negative 200 degrees Celsius, a simulated underwater depth of 5 miles, a drop from a height of 10,000 feet and then had them run over by a tank. There wasn't as much as a blemish.
  • Magical Defibrillator:
    • Amy restarts one of the Doctor's hearts with shock paddles. That is, of course, not what they do. On humans, of course; on Gallifreyans...
    • After a sizable fraction of humanity has been dead for a little while due to the cubes' effect, the Doctor uses them to restart the hearts of those affected. It's downplayed in that news reports mention emergency care being set up for those affected, implying some lingering ill effect.
  • Mundane Utility: The cubes spend so long doing absolutely nothing that people eventually take them for granted. Among other things, they've been put to use as paperweights, helping with in-door golf and something to leave notes on.
  • Noodle Incident:
    • The Doctor takes Amy and Rory to the Savoy, which is invaded by Zygons, and Amy accidentally gets engaged to Henry VIII.
    • The Doctor once ran a restaurant and invented the Yorkshire pudding.
    • One of Rory's patients at the hospital shows up in a wheelchair... with one of his feet stuck in a toilet. It's not the first time.
    • The Doctor, while playing Wii Sports, wonders what famous 1930s tennis player Fred Perry would say, and then says he'd probably want his shorts back.
  • Ominous Cube: Millions of small cubes suddenly fell to Earth one day, and remained dormant for a year, when they suddenly activated and caused one-third of humanity to go into cardiac arrest.
  • Patrick Stewart Speech: The Doctor gives a nice one in defying the Shakri's Tally:
    The Doctor: So. Here you are, depositing slug pellets all over the Earth. Made attractive, so humans will collect them, hoping to find something beautiful inside. Because that's what they are. Not pests or plague; creatures of hope. Forever building and reaching. Making mistakes of course. Every life form does. But. But - they learn. And they strive for greater and they achieve it. You want a tally. Put their achievements against their failings, through the whole of time. I will back humanity against the Shakri every time.
  • Pimped-Out Dress: Amy wears one briefly when they visit the Savoy. It has lots of lace, a nice sash and other decorations, like High-Class Gloves.
  • Power Trio: Discussed.
    Amy: It was also when we realised something the Shakri never could: what "cubed" actually means. The Power of Three.
  • Real After All: The Doctor was under the impression that the Shakri were a Gallifreyan myth.
  • Reverse the Polarity: The cubes turned human hearts off, so all the Doctor needed to do was hack into the cube's control hub and force them to turn the humans back on.
  • Rule of Three: Not only do we have the Doctor/Amy/Rory Power Trio, we have cubes. In mathematics, the cube of a number is the number raised to the power of three.
  • Shout-Out:
    • The Doctor likes to play Wii Sports.
    • A reference to Power Rangers RPM: When the Doctor gets his hearts going, he says, "Back in the game," and makes a pose — the exact same words and pose were used by Ziggy in the episode "Dome Dolls".
  • Sinister Geometry: The little black cubes appear in the billions all over the world. They are identical in every way and can't be destroyed by anything. Are they extraterrestrial, and if so, are they an invasion? No, they are an extermination.
  • Skewed Priorities:
    Rory: There are soldiers all over my house, and I'm in my pants!
  • The Slow Path: The Doctor still considers anything in excess of a few minutes The Slow Path. He gets intensely frustrated with boredom after a couple of days. After a chewing out from Brian about whisking his son and daughter-in-law off into the cosmos, the Doctor realises his selfishness and makes a better effort to stick around the Ponds' house.
  • Special Guest:
    • Professor Brian Cox appears, talking about the origin of the cubes.
    • Alan Sugar does an episode of The Apprentice where the challenge is to sell them.
  • Standard Snippet: During the scene in December with the patient with his foot stuck in a toilet, Slade's "Merry Christmas Everybody", a favourite of the show's, can be heard playing.
  • Title Drop: Amy does this in the final line. Both the actual episode title and the working title, actually.
  • Wham Line: "Why did you drop 'Lethbridge'?"
  • What Happened to the Mouse?: There were a number of people on the ship that exploded and we only saw the Doctor, Amy, Rory and Brian escape. It can be assumed that Rory and Amy were moving them out while the Doctor talked with the Shakri's hologram, but nothing is confirmed.
  • Writers Cannot Do Math: If the Doctor was telling the truth about how many times he kicked the football (five million), he would have had to kick it about 1,400 times per second to do it in roughly an hour. However, he had to have been kicking the ball at an exponentially faster rate than that, since he managed to squeeze in a whole bunch of other activities in that space of time as well. Maybe Rory's watch was wrong... or the Doctor's count was off. Lack of skill with numbers would suit him perfectly.
  • The X of Y: "The Power of Three". This is the 118th time the naming structure has been used in Doctor Who history.

Alternative Title(s): Doctor Who S 33 E 04 The Power Of Three