He feels John's body beside him, and, slightly fumbling, puts a hand on his shoulder - partly reassuring him, partly a gentle squeeze to ground them both.

The ongoing silence is only confusing for a moment, before he gets the taps on his bicep and his eyes widen briefly in recognition.

"Oh- Chell, hey-- come in." He moves to stand clear of the door, lightly tugging John clear too. "John, this is Chell, she's one of us. Another sign language user, but she can hear us perfectly fine. Chell, this is John Doe, he's from my world. My- my investigative partner."