first of all, as with most doctors, mayfield thought that his **** didn't stink. He felt he was above the law and could get a way with just about anything. thankfully that was not the case. what a shame it is to have to kill somebody to take credit for something that wasn't your project in the beginning. Then he tries to in a round about way blame Marsha for knowing more than shes telling.

All in all though L. Nimoy played the role perfectly. But Mayfield really caught himself in the end because when Colombo left, he could have easily gotten rid of those stitches before he came back in the room

One of my favorite Columbo lines. (not verbatim)

Mayfield "maybe she knows more than she's saying"

Columbo "actually sir I think she knows less than she's saying"

I've always liked the moment when Mayfield gets furious at Heideman for not telling him about being brought to the hospital by ambulance an hour before. I had a similar question about THE MOST DANGEROUS MATCH, but I always like to think of that as his last little moment of genuine concern for Heideman, instead of an act.

Mayfield's killing of Harry & framing him to look as though he had gone back to drug taking is maybe the most truly evil murder in all of Columbo.