The robot Nazi lets itself into Hitler's office, proceeds to activate its "justice mode" and spits a shower of light at the Führer. Inside the robot, one of the controllers suddenly realizes they've arrived several years earlier than intended. Before they can mosey on further up Hitler's time stream, though, the TARDIS comes crashing through the window and knocks the robot Nazi off its feet. The Doctor ushers everyone out of the TARDIS, urging them not to breathe the smoke. He also surreptitiously hides Mels's gun in a fruit bowl. No one will ever find it there! They eventually realize they've just inadvertently saved Hitler's life. Hitler makes googly eyes at the TARDIS. The Doctor takes the opportunity to make threatening noises like "the British are coming!" despite being squeamish about "foreknowledge" later in the episode. The robot Nazi rights itself, so Hitler starts shooting at it. Rory punches him out and grabs his gun. "Sit still, shut up," Rory says. Hot. He locks Hitler in a cupboard at the Doctor's suggestion.
Everyone turns their attention to the robot Nazi, whose controllers have made faint dead away in order to avoid discovery. The Doctor is suspicious of such a perfectly executed faint, but they have other issues to deal with. Like the fact that one of Hitler's shots got Mels right in the gut. As everyone rushes over to her, the robot controllers have just identified the TARDIS. A cute young controller says they've just found their biggest war criminal. "Forget Hitler," he says. "We take this one down and the Justice Department will give us the rest of the year off." Just when you think they're talking about the Doctor, the controller confirms for his captain: "It's her."
As Mels lies dying and everyone gathers around her, she waxes nostalgic about how she wanted to marry the Doctor when she was little. The Doctor promises to marry her if she lives. She tells him he has to ask for her parents' permission. You know, the parents that are right there in the room. Amy and Rory are all confused and then Mels starts glowing and the Doctor drags them away from her. "The last time I did this, I ended up a toddler in the middle of New York City," she says. The Doctor figures out that "Mels" is short for Melody, and Amy's like, yeah, I named my daughter after her, so then the Doctor's all yeah you named your daughter after your daughter! It's a whole Ouroboros thing. The timeline that ate itself. "You got to raise me after all," Mels says to the Ponds, which isn't really true. She explodes in regenerative light and then suddenly Alex Kingston is there.