"It was a random crime," the Doctor said with a sigh. "Something I could've prevented by thinking first. The thing that killed you was premeditated. The thing that killed Bea was, too. Those are the sort of things you should seek veng---justice for."

Vengeance was wrong. The Doctor needed to remind himself of that over and over again, but the image of Bea dead next to Jack was now burned into his mind. Something killed her. Something was chasing them. It was time they figured out what it was.