Close to death, Vincent Van Gogh is having a nervous breakdown, and has painted a picture as a message for the future: an exploding TARDIS. Winston Churchill, in his war room, has received a report that outstrips even his current concern with World War II: a painting has been found in occupied France of the TARDIS exploding. What shall he do with the message? He must deliver it to the future. He also tries to call up the Doctor, but his phone call is redirected to the Stormcage prison, where River Song is being held. When she gets Churchill's message, she escapes, going to find the royal collection of art of Spaceship UK, and finds the painting of Van Gogh's, guarded by Elizabeth X, future Queen of England. The Doctor and Amy are in the TARDIS, and the Doctor has had a great idea: decoding the oldest known written message in the universe. When he decodes it using the TARDIS' translation circuits, it says "Hello Sweetie", with a location: Roman Britain, near Stonehenge. Cleopatra is there, reportedly, but inside of a tent in a Roman camp, they instead find River Song, with the rolled up painting of Van Gogh's.
Cute opening titles.
Matt Smith as The Doctor. Karen Gillam as Amy Pond. Also, Alex Kingston as River Song, and reintroducing Arthur Darvill as Rory Williams.
The lengthy paragraph above describes just the opening of this, the first of a two-part season finale that is one of the more twisty, spectacular and momentous Doctor Who episodes of the revival. Since just the opening scene took that long to describe, a total synopsis of the plot would be difficult, and pointless, since as the cliche goes, it has to be seen to be believed.
Underneath Stonehenge, a unique artifact is buried: The Pandorica, a box that has sealed the most dangerous thing in the universe. While The Doctor is trying to figure out what horrible evil could possibly be sealed inside, and how it relates to the TARDIS' destruction, a collection of ships appears in the skies over Stonehenge: a coalition of all of the Doctor's enemies, coming to steal the super weapon that is the Pandorica. This prompts one of The Eleventh Doctor's most epic speeches, where he warns the alliance away just by reminding them of all the times he has defeated them in the past.
But for all of that grandeur, the end of the episode takes yet another turn: the being meant to be contained in the Pandorica, the "nameless, terrible thing, soaked in the blood of a billion galaxies", is the Doctor himself. The Doctor is locked inside an inescapable prison, just as outside, Rory, returned from non-existence as a Roman Solider, reveals himself to be an auton, a plastic robot duplicate, and shoots Amy. All seems to be lost, and Silence Falls, with no previews of what happens next week.