[ By this point, the Doctor was enjoying himself immeasurably. Whatever lingering annoyance had remained from the loss of his book, it had been far overtaken by the thrill of the chase and the only somewhat grudging admiration he got when he found someone who could give him a run for his money. The false wall had been an especially gleeful find, and after rummaging through that (no dice), he was now knocking on the others in search of more hollow spaces. ]

Oh, don't worry, if they charge you for it I'll make sure your roommate pays your half, too. [ beat, during which he knocks on another section of wall. ] It is your roommate that's responsible, right? I don't think anyone even knew you had a roommate, Kirei.