Columbo: Because that would explain why Miss Martin was so bothered after the operation, and it would explain why she wanted to see the chemist at the company that made the suture. That's murder. That certainly is. No question about it. (Mayfield starts laughing) What's so funny?
Dr. Mayfield: Excuse me, Lieutenant. I had to play it as though you were serious. You don't really believe all those foolish things you say, do you?
Columbo: (angrily slams carafe down on desk) I believe you killed Sharon Martin and I believe you're trying to kill Dr. Hiedeman.
Dr. Mayfield: Lt. Columbo, you're remarkable. You have intelligence. You have perception. You have great tenacity. You've got everything except proof.
Columbo: I want you to take good care of Dr. Hiedeman because if he dies, we're going to have to have an autopsy, aren't we? I mean, we're going to have to know whether a heart attack killed him or rather it was just dissolving suture.