The Eleventh Hour is the first episode of the fifth series of the revival of Doctor Who. It stars Matt Smith as the Eleventh Doctor, Caitlin Blackwood and Karen Gillam as Amelia/Amy Pond, and Arthur Darvill as Rory Williams. It was written by Steven Moffat, who was the new show runner. The title of the show is a reference both to the introduction of the 11th Doctor, the fact that the episode was an entire hour instead of the standard 45 minutes, and of course to the fact that the Doctor would once again save the world at the last moment.
The external backstory to the episode is as important as the internal story. After one series starring Christopher Eccleston as the Ninth Doctor, David Tennant had taken the role for three series, and his charm and youthful energy had established the image of the Doctor for the revival series. Tennant, as guided by Russel T Davies, was what people thought of as Doctor Who. In other words, Moffat and Smith had some pretty big shoes to fill. Matt Smith was also the youngest person to play the Doctor, and many people were curious how a 26 year old man would portray a 900 year old alien.
And we find out.
The story begins with The TARDIS crashing, and The Doctor finding himself in a small village, where he meets a young girl, Amelia Pond, who has a weird crack in her bedroom wall. After a post-regeneration dinner of Fish Fingers and Custard, The Doctor realizes his TARDIS has problems he must attend to. He also realizes that the crack in her bedroom wall is "Timey-Wimey", but he will be back in 5 minutes to fix it.
When he comes back to the village, he gets hit on the head by a tall, beautiful woman dressed like a policewoman. He also realizes there is an alien loose in her house. They escape, in true Doctor Who fashion, and start running through the village, when the Doctor realizes who this woman is: little Amelia Pond, all grown up. She has waited for a dozen years for her imaginary friend to return. This will be an important part of character information, but for now, The Doctor has aliens to foil. There is a prisoner loose, and an alien race called The Atraxi are going to either catch the Prisoner, or they are going to just go and incinerate the entire planet.
With the help of Amy's seemingly-wimpy fiancé Rory, The Doctor finds and defeats Prisoner Zero, and then, as the Atraxi leave, he calls them back, and lectures them, ending with a character-defining moment for the Eleventh Doctor, ordering them off the planet with:
"Hello, I'm the Doctor. Basically, run."
This being established, and after some more bad temporal driving, he invites Amy Pond into he TARDIS for future adventures.
The plot of the episode is more complicated than that, but the plot isn't important here as much as it sets up so much characterization. The episode is meant to introduce us to The Doctor and Amy, and it does that admirably. The Eleventh Doctor is both more crazy, more clueless and more militant and clever than his predecessor. The scene where he refuses all food given to him by little Amelia Pond, followed by his meal of fish fingers and custard, shows him acting the clown. Later, in the middle of trying to save the world with twenty minutes, the Doctor distracts himself asking why there are no ducks in the duck pond. And yet this same Doctor coolly lectures an entire alien fleet on just why it shouldn't cross him. By the end of this episode, Doctor Who fans were convinced that while there wouldn't be another David Tennant, Matt Smith was ready to build on the legend.
Although it is only hinted at in this episode, the dynamic between young Amelia (who will reappear in later episodes, both in flashbacks and in Timey-Wimeyness) is set up. Meeting the Doctor as a child, and then waiting many years for him to return, will give Amy Pond a different dynamic than any other companion.
In addition, there is so much symbolism and clues and hints in this episode that veteran fans, when returning to it, are amused. They are also still somewhat mystified. Time, perception, memory, identity and many other concepts that Moffat will be working on over the next two series (and presumably, even further) are all mentioned here, with varying degrees of subtlety.
Overall, it was a great season opener, a great episode, and was a sign of just how much awesome stuff was to be in store for us over the coming series.