Of all the monsters the Doctor has faced this year, the Daleks, dinosaurs and a trigger-happy cyborg, who would have fought that his most dangerous foe would be...a cube. As Earth is invaded by the mysterious 3D objects, the Doctor calls upon his closest companions Amy and Rory to help save the day. 'The Power of Three' was the best episode so far this year, an intoxicating blend of genuine horror and heart-warming dialogue that truly revealed it's not the Doctor that defines the show, but the friends that travel with him.

"The year of the slow invasion"

From Day of the Triffids to Invasion of the body snatchers, the home invasion is a staple of sci-fi horror, and with this year's episodes all taking place in fantastic far away places, to have one set on present day Earth brought the fear close to home. The six (seven) sided objects mysteriously appear one day littered across the planet, perplexing the populace, UNIT, and most frighteningly of all, the Doctor.

Similar to the ghost-like figures in the season two finale 'Army of Ghosts', the phenomenon very quickly goes from bewildering the public to being taken for granted. Showing the cynical side of human nature, the news outlets start questioning whether this is a stealth-marketing tactic. They've invaded both the real world and social media, as Kate Stewart explains to the Doctor, "Within three hours the cubes had a thousand separate Twitter accounts."

This is what makes the devices so terrifying. From being used as paperweights to makeshift targets for office golf, the cubes are everywhere; in everyone's homes the world over. Patiently watching, waiting, the cubes gather all the information they can about the human race before deciding to strike.

The Lodger

This invasion of the home by the alien objects is mirrored to that of the Doctor, who at whim crashes into the Pond's life to take them on his adventures. Dismissive of their life at home, the Doctor is shocked to find Rory and Amy have jobs, saying that he imagined they spent their time without him, "mostly kissing". Whilst Rory heals the sick, even Amy has a sensible job now, using her experience of journeying through time and space to write travel articles. Rory notes that they can't abandon their commitments at home whenever the TARDIS materialises, as he tells the Doctor "What you do isn't all there is." The two decide to commit to their own lives at home, and in a neat twist the Doctor is forced to join them.

Similar at first to 'The Lodger', a frustrated Doctor decides to live with the Ponds and wait for the cubes to make their move. Like an impatient child, he throws a tantrum when he finds there's nothing to do and proceeds to engage in an assortment of activity from football keepy-uppies to painting the fence. Amy says to the Doctor that, "the travelling is starting to feel like running away". She sees their travels with the Doctor as fun escapism from the realities of life and the whole host of commitments that normally tie us down. We as viewers tune in every Saturday night for the same reason, to escape our own lives for 45 minutes whilst we witness the adventures of these characters across time and space.

In a poignant scene on the bank of the River Thames, The Doctor explains to Amy, "I'm not running away from things, I am running too them before they flare and fade forever". Ever since the Doctor regenerated into Matt Smith's current incarnation, Amy has always been there by his side, to the extent where he can't imagine travelling without her or Rory. Doctor Who isn't defined by its adventures but the companions who travel with the alien hero. And with that being the case, the Ponds will be sorely missed.

"One day, soon maybe, you'll stop."

With Amy, Rory and the Doctor united once more, 'the power of three' defeats the cubes by reversing the cardiac attacks they had caused the world over. After all the mystery of what the cubes were and what their purpose was, the revelation that they were simply weapons used by the Shakri, the pest control of the solar system, was decidedly underwhelming. But to dismiss the episode's flimsy finale is to forget how enjoyable the story up until that point was, and of the extremely satisfying emotional climax that's reached when Amy and Rory decide that their lives should be with the Doctor until as the Time Lord notes, "you fade from me".

The ominous tones to that line seem to foreshadow that something bad will happen to the happy couple in what we know will be their last episode next week. They can't die, can they? The Doctor admits to Brian it's happened before, adding a further sense of jeopardy for next week's finale, when the Angels take Manhattan.

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