Down on the planet's surface, the Doctor notices that Trenzalore is covered in a giant battlefield graveyard. (He cracked a window pane on the ship, too. Whovians, is this the first time we've seen the TARDIS noticeably damaged under assault?) The Doctor explains that the biggest gravestones are reserved for the highest-ranked soldiers. They look up and see a giant TARDIS -- it's enormous. And it's his TARDIS, what's left of it. When it dies, "all the bigger on the inside starts leaking on the outside."
River Song appears! It's a wonderful tendency of hers throughout the episode. She claims the Doctor won't be able to see or hear her, though Clara will because River has maintained the psychic link from their earlier "conference." The Doctor sees River's grave, which shouldn't be right? Except that she's dead -- "should have mentioned that," he says. It's a long story involving a library, but her grave can't be here. The white-skinned men appear again, as if they're omnipresent. Maybe it isn't a grave, River whisper-says to Clara, who shout-says it to the Doctor. Maybe it's a secret entrance. It is a secret entrance, and down the Doctor and Clara fall into it, alongside the revelation that River song is the Doctor's wife.
Inside the giant TARDIS husk (sad face), Strax and Vastra are alive and awakening. Jenny, however, is still dead, though Vastra gets Strax to remedy that with an "electro-cardio restart" to her shock-stricken heart. This allows for a lovely couplet of conversation, as the lizard woman holds her once-dead human wife. Strax says, "The heart is a relatively simple thing." Vastra responds, "I've not found it to be so."
The white-skinned men appear again, circling the trio. Leading them is Dr. Simeon, who we last saw dying at the end of Christmas special "The Snowmen." Ah, he's dead, but the omnipotent parasite that he served isn't. That's who this is: The Great Intelligence. "Welcome to the final resting place of the cruel tyrant, of the slaughterer of the ten billion and the vessel of the final darkness," Simeon says, "the tomb of the Doctor." Lightning strikes! But know that there will be parsing of this leitmotif to come.
Clara and the Doctor are scouring through some catacombs (Clara hates catacombs) while also unraveling the mystery of how River is even alive, kind of. She isn't: After the events of "Silence in the Library"/"Forest of the Dead," a much earlier Moffat two-parter, the Doctor preserved River's spirit/consciousness in a database in the largest library in the universe and then left her there "like a book on a shelf." Didn't even say goodbye (endings, understand).
At Dead TARDIS Central, Vastra, et al. are still questioning TGI about its plans. He knows so much about the Battle of Trenzalore -- it was a minor skirmish by the Doctor's standards, no Time War, but still enough -- and about the Doctor's bloody past because he is information. Literally, TGI rips back Simeon's face like a peel to reveal that his body is hollow. It collapses but in a moment, TGI has jumped to one of the white-skinned men transformed it into another Dr. Simeon. Neat.
NEXT: "What were you expecting: a body?"