Chell's eyes were tracking every single movement Zach was making, ready to pull the trigger at any given time. As he was extracting the notebook from his pocket Chell noticed him dropping that paper ball, but did not pay much attention to it. Her brain was rationalizing the situation like this: Zach is mute, this Zach person talks, high chance of this not being the actual Zach. But as he wrote down on the paper 'Happy now?', Chell relaxed, recognizing the handwriting. She slowly lowered her rifle, but kept her finger on the trigger.
"Yes. Thank you, sir. My apologies." she gently muttered before turning on her toes and walking a bit further down the road, where another lit house was. With an almost identical motion she stepped in front of the door and vigorously knocked 3 times.