A janitor opens the door from the outside, he is not wearing glasses. The scene from inside the room shows the janitor now wearing glasses.
Perry and Paul Drake drive up to the lake to inquire about the dead body. The passenger vent window on the Cadillac convertible is open when they exit the car. When they return to the car the vent window is now fully closed.
Perry is awakened in the middle of the night by a phone call, but when they show the caller in a phone booth, it is obviously daytime.
The murder victim is found in a closet of his home, standing upright. Rigor mortis can stiffen a body lying supine at its onset, but the body will never be able to stand unsupported.
After inspecting an ejected cartridge casing, Perry says it was probably fired from a Beretta; rarely is it possible to tell the make of a gun from its ammunition.
A character is called Abigail Esther Leeds throughout the episode, but her name on a birth certificate is shown as Abigail Edith Leeds. However, it is not unusual for a person to use a name other than their given name, especially if they haven't seen their birth certificate (which was not uncommon prior to the latter part of the 20th century.
Paul calls Perry on the phone as a prearranged signal, letting the phone ring twice and then hanging up and calling again. When Perry receives the signal, the pause between phone calls is only about two seconds, not long enough to dial a number with an old-fashioned rotary phone.
Perry and Della are searching an office and hide on a fire escape outside, when Tragg and another detective are about to come in. The two detectives soon conduct their own search, and Perry and Della take this opportunity to climb down the fire stairs. The janitor who let the two detectives in is still present and can see Perry and Della, but says nothing.
The supposed nighttime shots of Paul outside Tydings's office while Perry and Della are inside obviously were done during the daytime with a filter. There is a lamppost in front of the office building, but no light is shining down from it onto the street. There is also a shadow from the building behind the camera covering half the street, and when Tragg's car pulls up, its headlights aren't on.
When Perry and Paul arrive at Westside Lake, the black & white patrol car they pass has no city emblem or markings; just a plain white door.
The front door of Perry Mason's apartment has no lock. Neither on the doorknob or a deadbolt.
Perry enters his office from the hallway door that Paul usually uses. As he's closing the door behind him, a hand outside the door can be seen reaching for the doorknob to either close it the rest of the way or hold it closed.
When Perry and Paul discover the dead body, Perry says that the dead man isn't the same man who 'came to his office' last night. Late last night, however, Perry was at home, so a man and his veiled lady companion came to Perry's apartment, not to his office.
The secretary in Tydings' office tells Perry he has a phone call and that he can take it at the other desk on line two. Perry picks up the phone and says "hello" before he pushes the button to open line two.
When Perry and Paul have finished their investigation of the sunken car at the lake, Perry puts his arm on the back of the car seat and turns backwards, as if he is going to back up, yet when the car starts to move it goes forward about 18" before the camera cuts away.
(at around 17 mins) Paul Drake and Perry Mason discover the dead body of Albert Tydings. Using the nearby house phone to call police, both Perry and Paul handle the phone with bare hands, a serious breach of possible evidence preservation.