When they were up in the sky tram at the end, Roger opened the doors on the side, presumably to try and throw the cigar box out. When he's on the floor gathering up the cigars, the doors are closed, but when they show Columbo and Logan, the door is open again. When Roger puts the necklace on Columbo, the doors are closed again.
When Roger Stanford arrives at David's office, the suitcase and coat were already there and when he is in David's office you hear Quincy saying its almost six o'clock. But when Columbo was in Miss Bishop's office he said someone told him the items were dropped off at six o'clock. Clearly this is incorrect, since the items were already there before Roger arrived.
(looking at the cigar Columbo is about to light up)
Logan: Oh, aren't those supposed to be evidence, Lieutenant?
Columbo: See, now there you go. You're looking at your watch again.
Roger: Will you do me a favor? Will you please keep quiet?
Columbo: Why? It's only a dumb theory of mine.
Columbo: You know something, Roger? The truth is hard to find sometimes. Sometimes it's right in front of you and you can't prove it.
Columbo: Now you see, my problem with Chemistry, that started way back in high school 'cause in my junior year I, I had to get a better grade. So I said to heck with this Chemistry stuff. I'll take another year of wood shop. You know, you just build a birdhouse and if you paint it red you get an A.
Doris Buckner: Roger, I called the commissioner of police, and he said he's send over his very best man.
Roger: Is that a fact?
Columbo: Well, my wife says I'm second-best, but, uh, she claims there are 80 fellas tied for first.
Original script title: "Formula for Murder"
William Windom is billed as Special Guest Star.
90 minutes long.