At first, William's only response was a sharp intake of breath and to sit there stunned. Celia. His daughters. He'd sympathized with Tyrith when he'd heard about Toria's kidnapping. Of course, by the time he'd heard of it, she'd been returned safely. Only now could he truly empathize with how his goodbrother felt right at that moment. He wanted to find everyone who meant his family harm and slay them all, then take his family back to Winterfell where everything was safe and made sense.
He put his head in his hands for nearly a minute. The tension was there, and by the end of the day, he was sure that he'd have a headache.
"I thank you for telling me this in private," he said at last. "I want them found, and anyone who harms any of them..."
He let that trail off. He wanted to deal with them the northern way, but could he trust himself to be stoic if he was faced with a man who had killed his sister or his daughters? He wasn't certain.