Chell staying silent for a long long time, even with Doug, even after they've lived through the hell and back together. First, as always, out of her stubbornness, but after because she's anxious to break the silence and mess something up. Oh no, she won't mess this up. When she finally says something Doug is understandably spooked. A voice! Maybe one of his voices, he has no way to know for sure. Chell doesn't apologize, she just asks how she can help. So Doug tells her it would be good to touch her lips, to feel them move as she speaks. And she lets him, of course. Yeah.