Quote from : Mortal Coil Book

Valkyrie Cain got out of the passenger side. She zipped up her black jacket against the cold, and joined Skulduggery as he walked up to the front door. She glanced at him, and saw that he was smiling. "Stop doing that,” she sighed. “Stop doing what?” Skulduggery responded in that gloriously velvet voice of his. “Stop smiling. The person we want to talk to lives in the only dark house on a bright street. That’s not a good sign.” “I didn’t realise I was smiling,” he said. They stopped at the door, and Skulduggery made a concerted effort to shift his features. His mouth twitched downwards. “Am I smiling now?” “No.” “Excellent,” he said, and the smile immediately sprang back up.