Spoilers so definitely lie ahead. Do not say I didn't warn you and get all pissy in the comments section. Skip to the end if you don't want an episode summary.
Here's the breakdown:
We start off with a crop circle which says, "doctor," - Amy and Rory's way of grabbing the Doctor's attention and getting him back to Leadworth. Unfortunately, he has no clues as to the whereabouts of Baby Pond. Sirens approach in the distance and soon appears Mels, best friend of Amy and Rory, hotly pursued by the Leadworth police. She hijacks the TARDIS at gunpoint and demands to go kill Hitler (and really, who doesn't want to?).
So off we are to Nazi Germany, where Hitler is already under attack. Not by the British (not yet anyway, it's only 1938) but by a robot filled with tiny people, disguised as a Nazi! How cool. They are a time traveling evil tracking machine intent on killing Hitler for his unspeakable crimes against the universe. No arguments from me, except the Doctor might tell you that it's fixed that Hitler always is a mass-murdering f***head, as many famous historians have said.
The TARDIS crash-lands into the robot, inadvertently saving Hitler from the tiny time travelers, and placing our squad in a rather odd position. When the robot gets up, Hitler freaks and tries to shoot it, but he's apparently a horrible shot because he hits Mels. Oh noetry! But wait, Mels starts...regenerating? You say what now? And she regenerates into...River Song?!? At this point I'm practically inches from the screen.
(amazing one liner moment - "Shut up, Hitler!")
Then begins the dance between Mels/Melody Pong/River Song and the Doctor as she tries to MURDER him. We find out that she did not escape the clutches of the Silence soon enough and she was brainwashed into being an assassin with only one target - The Doctor. She hasn't even heard of River Song. Definitely mixed emotions here - this is a character we've come to know and love, moreover, the Doctor has come to know and love this person. Everything's gone all topsy turvy. The Doctor is able to match each of River's attempts on his life until she kisses him and heads towards the window. Confused for a moment, the Doctor suddenly falls - she's poisoned him. Devotees will remember River's hypnotic lipstick. Guess she has a more potent brand as well.
Amy and Rory chase after River while the Doctor heads to the TARDIS. Amazing one liner moment as River confronts armed Nazis. The Doctor discovers in the TARDIS that there is no cure and that his regeneration has been disabled. Meanwhile, Rory and Amy get sucked into the robot time machine, finally given a name - The Teselector (sp?) - and River sends a bunch of German bougie diners running away in their undergarments. The crew aboard the Teselector have acknowledged Melody Pond/River Song to be the killer of the Doctor and are hunting her down now in the form of Amy and they find her in the restaurant. The Doctor soon joins with his TARDIS.
So the climax of the episode, here it is. Final showdown between the three forces at work - Doctor, River, and the Teselector - Doctor still dying. Amy saves her daughter by turning the Teselector's defense against the crew and River in turn, moved by the Doctor's will to help his friends, saves Amy and Rory by flying the TARDIS into the Teselector to retrieve them. She says the TARDIS showed her how to fly it and that she is the daughter of the TARDIS. They hurry back to the Doctor, who says nobody can save him. He asks Mels/Melody Pond/River Song to give River Song a message, which he whispers in her ear, inaudibly. Then he dies.
Shocked, Mels/Melody Pond/River Song stands back and asks who River Song is, only to be shown it is in fact her. She uses her remaining regeneration energy to bring the Doctor back to life. Thus River Song has killed the Doctor. And River Song has brought him back to life, but at a cost - she used all her remaining regenerations in that one selfless act. They leave her in a hospital to heal as they continue their search for the infant Melody Pond and the order of the Silence. The Doctor gives her a TARDIS-blue notebook, brand new and wrapped in red ribbon. We last see River applying for a position as an archaeologist.
COMMENTS:
Okay, so like I said, a lot of questions brought up here. The one that it really left me with is, "Is River Song still out to kill the Doctor?" The way the episode ends you can't really tell. River says she wants to get into archaeology to find someone, obviously the Doctor, but its difficult to tell if that smile is one of an assassin or not. Something that we will clearly find out though.
We also know a bit more about the Silence now. They aren't just a creature, it's a religious order who believe, "that Silence will fall when the question is asked." But nobody knows what the question is! Definitely something for the internet forums - I'm sure they're all aflutter with theories. All I know is that the answer is 42.
This episode also provides a truly great character moment for the Doctor. When he is dying inside the TARDIS and asks for an interface, he's first given a hologram of himself to which he responds, "No! Give me someone I like!" The moment is glossed over, but I really want to call attention to it because that is huge. He doesn't like himself. I'm not saying this is brand new or anything, but here he is, plainly saying it. Big character moment.
So definitely a 10/10 for this one. Please note in the comments if there's anything here you want to hear more about!