He took the offered thought, added it to his mind as he did everything else that happened. On the question, he could honestly smirk and look at Voldemort. "Look again," he answered, because of course he had only left the man in order to allow Snape his turn.
The man's mind had been broken after that encounter. He'd descended into complete and utter insanity. His seemingly completely lifeless body had been dumped at the doorstep of a Muggle hospital with the firm knowledge that the man would never be found. The memory of said lifeless body was true even if the part where he was still breathing was hidden.
He showed the Dark Lord the victim, in his dungeon, not remorseful at the slightest. "Sometimes slow is more sweet than fast. I wanted him to know why he was there, to worry and fear what would come. Waiting can be the worst kind of torture."