"Hey, Angelo? Christian? Where are you?" Bob walks headlong into bullshit. Even that name, Evangelista, links her back to this story, doesn't it? That's weird, obviously not on purpose, but funny that years later we'd revisit this particular story architecture with a xeroxed Evangelista character sewn in, when just by her name she could have been a member of this squad.
"The maze is on six levels," it's explained as they work their way upwards, "Representing the ascent of the soul. Only two levels to go." The Doctor offers to take Amy to visit the Aplans in their prime, and for some reason she forgets they are time travelers. "I thought they were all dead?" He says he bowls with Virginia Woolf, too, and then either makes a weird joke about her ("Very relaxed, sort of cheerful") or goes back to talking about the Aplan: "That's having two heads. You're never short of a snog with an extra head!" While River starts to figure out something is dreadfully the matter, and the Doctor agrees, he continues to hector Octavian: "Then they had laws against self-marrying and what was that about? But that's the Church for ya!" Octavian bristles, as the Doctor meant him to do, and they keep searching, and Amy sort of apologizes for him: "Church had a point, if you think about it. The divorces must have been messy..."
River and the Doctor get real annoying at this point, making encoded exclamations and patting each other on the back for having figured it out, without actually saying what they've figured out, until everybody is annoyed. See, the Aplan had two heads, but all the statues have one head -- maybe they didn't notice because of yet another "perception filter," or maybe just because the plot often requires that intelligent people act like total buffoons. So essentially, without explaining a goddamn thing as he twist-twist-twist ratchets up the tension of the scene, the Doctor gears everybody up to total hysterics while apologizing for, still without explaining, the trap into which he has led them. Then he makes everybody turn off their flashlights, which wigs everybody out, and turns his back on. And guess what? All the one-headed statues in the entire cavern have gotten closer. Got it? No? "Clerics, keep watching them. Every statue in this maze, every single one, is a Weeping Angel." And they are being hunted.