The Power of Three (TV story)

 was the fourth episode of the seventh series of Doctor Who produced by BBC Wales.

Synopsis
There have been many ways to invade the Earth, and the Doctor has seen them all – or so he always thought. And then the human race wakes up one morning and discovers the world has been overrun by… "very small cubes", which then proceed to… do nothing at all. A plan is afoot, humanity is endangered – but by what and how and, above all, when? Thus begins the Year of the Slow Invasion.

For the first time in his world-saving career the Doctor has to call upon one of the least of his virtues: patience. And the Ponds face something possibly more terrifying than any world-ending apocalypse: the Doctor is moving in!

Plot
After realising that they lead two lives, their "Doctor" life and their everyday life, Amy and Rory conclude that they should choose one to stick with; but then are whisked away on another adventure with the Doctor. After returning home, the couple settle back into routine.

But one morning they are by Rory's father Brian, who alerts them to the global appearance of small, black cubes. The Doctor, already there, quickly attempts to understand them. His experiments accidentally attract the attention of U.N.I.T. and a strike team quickly responds. After the team locks down the couples flat, Kate Stewart arrives on scene and identifies the Doctor. She and the Doctor wish to continue monitoring the cubes, as it appears that due to the cubes' inactivity people have started taking them home and to work. U.N.I.T. departs as does the Doctor, leaving Brian and U.N.I.T. monitoring the majority of the inactive cubes.

Several months pass, with Amy and Rory taking on the commitments of everyday life. During their anniversary, the Doctor returns to take the couple on a journey through time once again. The trip takes on the usual mishaps; a few days journey turns into seven weeks. They return to the moment they left, and Brian questions the Doctor about the fates of his past companions; worrying about the Ponds possible future travelling with him.

The next day, among everyday life, the cubes activate. Every effect is random, and the cubes inside the the Ponds' flat also activate. Around the world, many of cube's effects are dangerous. Rory and Brian leave to help the hospital with the recent injuries, and the Doctor and Amy are summoned by U.N.I.T. to the Tower of London. Captured cubes exhibit different effects; such as hacking national defence systems around the world. Soon the cubes become inactive again; the world begins to recover.

At the hospital, Brian crosses paths with two identical "nurses", in reality non-human entities being used by a small girl holding an active cube to kidnap patients from the hospital. Having been discovered, Brian is kidnapped as well. Outside the Tower, the Doctor and Amy debate the merit of travelling the way they do; Amy considers it "running away" and the Doctor considers it "running to". During their conversation, the Doctor realises the cubes acted out to gain attention and scan the entire planet.

The power at U.N.I.T. goes out, and the cubes start a countdown from seven. At zero, the cubes open but contain nothing. Moments pass when around people suffer fatal heart attacks, with the Doctor experiencing heart failure with one heart. He and Amy leave for the hospital, where Rory notices his father's absence. The Doctor discovers the little girl with the active cube and reveals her to be a simple android overseeing the entire operation. The Doctor shuts her down and Amy restarts the Doctor's heart with a defibrillator.

The Doctor and the Ponds converge on board a spaceship through a wormhole in a "Out of Order" elevator. The two "nurses" are on board and are quickly disabled. Brian is taken back to the hospital by Amy and Rory while the Doctor meets the ship's on-board hologram. The ship was built by the Shakri, which in the Doctor's opinion are the "pest controllers of the universe". The stolen electricity was used to exterminate the human race; which the hologram thinks is a contagion to be destroyed. Returning to the ship, Amy and Rory watch the Doctor reuse the electricity to start the stopped hearts on Earth. The surge, however, destroys the Shakri ship just after the Doctor and the Ponds escape. Later that night, Brian urges the couple to continue to travel with the Doctor, believing that they should enjoy the opportunity to change the world.

Cast

 * The Doctor - Matt Smith
 * Amy Pond - Karen Gillan
 * Rory Williams - Arthur Darvill
 * Brian Williams - Mark Williams
 * Kate Stewart - Jemma Redgrave
 * Shakri - Steven Berkoff
 * Ranjit - Selva Rasalingam
 * Laura - Alice O'Connell
 * Arnold Underwood - Peter Cartwright
 * Orderly 1 - David Beck
 * Orderly 2 - Daniel Beck
 * UNIT Researcher - David Hartley

Uncredited cast

 * Brian Cox - Himself
 * Lord Sugar - Himself

Communication technology

 * Kate mentions Flickr, YouTube and Twitter.

Game consoles

 * The Doctor plays tennis on the Nintendo Wii.

Music

 * The song "Merry Xmas Everybody" by the rock band Slade is briefly heard in the hospital.
 * One of the cubes plays the "Chicken Dance" song (aka "The Birdie Song"), on an endless loop. The Doctor seems annoyed.
 * The song "Titanium" plays at the party Amy attends.

Culture

 * When Amy calls the Gallifreyan bedtime story about the Shakri weird, the Doctor remarks, "You can talk. Wolf in your grandmother's night dress?" in reference to the story Little Red Riding Hood.
 * The Doctor tells Amy, "Through the looking glass, Pond," in reference to Through the Looking Glass by Lewis Carroll.
 * The Power of Three could be a a veiled reference to the American television series Charmed where the power of three witches known as the Charmed Ones combined is referred to as The Power of Three.

Energy and radiation

 * Kate traced Artron energy levels to find the Doctor and then identifies him due to his fashion sense and binary vascular system.

Foods and beverages

 * The Doctor states that he invented the Yorkshire pudding.
 * The Doctor, Amy and Rory eat fish custard.

Individuals

 * When Brian asks the Doctor what happened to those who previously travelled with him, he tells him that some left him, some got left behind, and some died.
 * Amy accidentally marries Henry VIII.
 * While playing virtual tennis, the Doctor mentions the tennis player Fred Perry and a pair of shorts he borrowed from him.
 * The real physicist Brian Cox plays himself as he is interviewed on the news for an opinion about the cubes.
 * Amy estimates that she and Rory have known the Doctor for ten years in their personal timestream.

Species

 * There were Zygon duplicates at the Savoy when Amy, the Doctor and Rory visit.

Regeneration
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 * The Doctor states that he keeps returning to Amy because she was the first face his eleventh incarnation laid eyes on

Story notes

 * For this episode, the Doctor Who logo's texture resembled the cubes featured prominently in the episode.
 * The working title for this episode was Cubed.

Ratings

 * The episode received an overnight viewership of 5.49 million people in the UK.

Filming locations
Belle Vue Park, Albert Road, Penarth (filming took place on June 28 2012)

Production errors

 * After Kate Lethbridge-Stewart enters Amy and Rory's house, we see her take out her scanner. When she originally takes it out, her screen is facing the Doctor, and in the next shot, it is facing away from him.
 * In some shots when the cubes are counting down from 7, some cubes are missing the numbers in one shot and then have them in the next.This can be seen at 28:01 when the doctor is in the room with the cube, and when the nurse is removing the cubes from the hospital at around 25:44

Continuity

 * Rory's father Brian reappears. (TV: Dinosaurs on a Spaceship)
 * The Eleventh Doctor, Amy and Rory have fish custard. (TV: The Eleventh Hour)
 * Kate Stewart is the daughter of Brigadier Alistair Gordon Lethbridge-Stewart. (HOMEVID: Downtime, Dæmos Rising,The Scales of Injustice)
 * The Doctor, talking to a flying cube, says, "Is that all you can do? Hover? I'd a metal dog that could do that", referring to K9. (TV: The Wedding of Sarah Jane Smith)
 * The Doctor once again asks how humans cope with just one heart. (TV: The Shakespeare Code)
 * Twitter is mentioned again; the Doctor seems similarly unimpressed. (TV: The Girl Who Waited)
 * The UNIT base beneath the Tower of London is visited. It was previously mentioned in TV: The Christmas Invasion and The Sontaran Stratagem.
 * The Ponds' anniversary takes place. They were married in Leadworth on 26 June 2010. (TV: The Big Bang)
 * A voice interface was last seen in TV: Let's Kill Hitler.
 * Rory kisses the Doctor on the cheek. The Doctor previously kissed Rory on the mouth in a moment of excitement. (TV: Dinosaurs on a Spaceship)
 * The dress and hairstyle of Amy during her visit to the Savoy Hotel is similar to Tegan Jovanka's dress and hairstyle at the party's Shadow. (TV: Enlightenment)
 * The Doctor unintentionally reveals his hiding place to Henry VIII by sneezing. In a previous adventure, whilst hiding from another royal, Charles II, he gives away his location by sneezing. (TV: The Impossible Astronaut)
 * Whilst hiding from Henry VIII, the Doctor is holding a mobile phone charger, which is apparently dropped as he sneezes. (TV: A Town Called Mercy)
 * The Doctor mentions that he's run restaurants before. (PROSE: The Crystal Bucephalus)
 * The Doctor tells Brian that companions have left him, (TV: The Last of the Time Lords, et al.) been left behind, (TV: The Dalek Invasion of Earth, et al.) and a very few have died. (TV: Earthshock, et al.)
 * A defibrillator has been used on the Doctor before. (TV: Doctor Who: The Movie)
 * Although he hates it, the Doctor gave a salute to Kate, like the Tenth Doctor when he was reunited with the Brigadier. (COMIC: The Warkeeper's Crown)

DVD releases
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Blu-ray releases
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