Sentence:  He's a stone-cold snake, Nick, but he's our stone—cold snake. Keep tugging on hanging threads and one day your pants will fall off." / Nick did a <WSD>take</WSD>, grinning in spite of his miserable mood. “How, exactly, would that work?" / Mavis shrugged, grinned right back at him. 
Meaning of the word marked with <WSD> tags:  A visible (facial) response to something, especially something unexpected; a facial gesture in response to an event.