[Clara's silent for a moment, eyes pointedly avoiding River's. God, she feels so childish and petty. River thinks she's going to succeed where everyone else here has failed for months, and part of Clara is just itching to prove the flaw, to hold it over River's head and win. But win what, exactly?]

... We have access to very little of the station, and it seems to be intentional. Even the maintenance shafts only go so far before you're blocked off. There's a hangar, but nothing in it that could take anyone very far. Some people have been down to the planet, but it's much the same as here. And... [Oh, this is the worst part, the one that makes her feel weak and childish and scared.] ... they can get in our heads. In our bodies. People have heard voices, had weird stuff happen to them. A friend of mine- ... this place killed him, and then brought him back.

[She looks down at the floor, and then up at River, only pulling in a breath to speak again - ] I think we're an experiment.