Apparently all it took to ruin his morning was one simple word directed at him. Dad. His mind couldn't even try to sort out if she was telling the truth or not. The "bollocks" that slipped from his lips was reflexive. While Zacharias Smith had a decent amount of sex, the past week withstanding, he always stayed up to date on his contraceptives because he was not keen on becoming a father anytime soon.
Except sometimes there were accidents and the potion didn't always work.
"You're just..." Zacharias shook his head. "I'm not doing this." He turned back to the door. And unless she tried to stop him, he was just going to head back to Peebles. There was already enough for him to deal with and then she went and said that.