Hold that tongue. The detective should know better than most that he was already too far down the rabbit hole even before all that. No need to rub it in and make him feel any worse. If he could still feel worse and not apathy. "I... I see. It is kind of a pity. Things get in the way, I suppose." Like bodies. "But I think the both of us have learnt something from it?"
"How ironic," he muttered. "I'm not supposed to be teaching you anymore."