A Good Man Goes to War is the seventh episode of the sixth series of Doctor Who, and was the mid-series finale and cliffhanger. It starred Matt Smith as The Eleventh Doctor, Karen Gillam as Amy Pond, Arthur Darvill as Rory Williams, and Alex Kingston as River Song. It was written by show runner Steven Moffat. The episode is listed as being a two-parter, but the second part, Let's Kill Hitler, is not a direct continuation of this episode.
Spoilers!
Trying to search for a pregnant Amy Pond, the Doctor and Rory tear through the universe, putting together a team to find the people who have kidnapped her. This includes the Spitfire pilots from Victory of the Daleks and the pirates from Curse of the Black Spot, as well as Madame Vastra, a Silurian from Victorian London, and her lover Jenny. But River Song refuses Rory's request to bring her along. The Doctor finds and infiltrates the base of Demon's Run, where Amy and her baby Melody are being held captive by a mysterious alliance. The Doctor quickly overcomes and defeats the forces there, making true the proverb that "Demon's run when a good man goes to war".
The battle scene is epic, showing The Doctor at his most inventive, devious, and, for lack of a better word, macho.
"Good men don't need rules. Today is not the day to find out why I have so many."
The action scenes are convoluted, fast-paced, and use the full scope of the program, something that Moffat has been good at, especially in this sixth series.
After the emotional thrill of the Doctor's victory, we are then brought low again: Eyepatch Lady, the mysterious kidnapper of Amy, smirks at the Doctor and tells him she has fooled him twice with the same trick: the baby Melody they have rescued is a duplicate. She still has the real Melody. Just as they realize this, River Song shows up. Her and the Doctor have a conversation where he realizes something, and runs off. Amy, Rory and (possibly the audience) are confused, until River tells them the truth: she is Melody Pond. Shock abounds, unless you already guessed this plot twist weeks ago.
The episode is suitably epic, being both a special effects based science-fiction episode and a character study into the nature of The Doctor: it is brought up explicitly whether The Doctor is a healer or a warrior. The mystery of just who kidnapped Amy is still left for later in the series.
This episode is suitably grand, although some (myself included, at times), thought that at some point Series 6 became an exercise in seeing just how many plot twists could be thrown in, to see just how much the viewer could be misdirected. Is River's tearful reunion with her parents a moment of pathos, or is it just melodramatic, because the characters haven't been developed, but are just being moved around like pieces on a board by a demented chessmaster? The opinions of Doctor Who's fanbase is very divided on this question.