Goofs

In the initial long-shot when McPherson and Lydecker are out to dinner, McPherson's chair is unoccupied (about 15:28). When the camera is at their table, McPherson has materialized.

When Lydecker is talking to Laura about Carpenter, he reaches for the file twice.

When McPherson first interviews Mrs. Treadwell, the position of his elbow changes between shots, from being up to resting on his leg.

When McPherson is seated talking to Carpenter at the country house, his position in relation to Carpenter changes between shots.

When Shelby arrives at Laura's apartment and is greeted at the door by Mark, he tosses his hat onto the small table just off screen. From the shadow it's obvious that he misses, and his hat falls onto the floor. No one reacts to this, and they continue the scene as intended. When Waldo arrives at the door a short time later, the hat is nowhere to be seen.

When McPherson finds the shotgun, he breaks it open and pulls out the shells with his bare hand possibly negating any fingerprints. Then he replaces the shotgun in its hiding place at Laura's and says he will come back for it the next morning. As it is crucial evidence he would have taken it with him rather than leave it behind and lose the chain of evidence and risk it disappearing as he knows Lydecker was trying to recover it.

When Laura first tries to get Waldo to endorse a fountain pen, she holds the advertisement in front of her when they both are in the shot. When the shot changes to her alone, the advertisement has shrunk significantly in size. The advertisement resumes its original size moments later when both Laura and Waldo are in the shot together. In the solo shots Laura is holding the card in front of her and the shot includes only the top of the advertisement board which is rectangular and longer than it is wide so only the narrow top shows.

When McPherson and Lydecker are in the restaurant, Lydecker says he and Laura were at the same table on the night before her 22nd birthday. He then says they met 5 years earlier when she tried to hire him to endorse a pen for an advertising company where she worked. That would make her 17 years old and working in a professional position. It is not clear whether Lydecker is referring to five years before he is talking to McPherson or five years before them sharing the table before her 22nd birthday. At the time they met Laura was working in the stenographic department at a small desk in a junior position pasting photos when Lydecker drops in to visit her.

When McPherson goes to Lydecker's, he is nosing around with some of his art stuff and picks something up. Lydecker tells him to leave it alone or some such, as it is priceless and not to break it. However, it will be seen that Lydecker is in the bathtub, and the door is nearly completely shut; he could not have seen McPherson doing anything from that vantage. Note that there was noise as McPherson opened the case and picked up the glass object that Lydecker could have heard. It is possible that Lydecker could see from the tub out the open door to the artifacts' case or have recognized the noise he heard as the artifacts' case being opened.

Waldo Lydecker mentions that Lt. McPherson was wounded at the siege of Babylon, Long Island. An NYPD officer would not normally respond to calls for service in Long Island.

However, it's possible that McPherson come to the NYPD after serving in Long Island.

Ann Treadwell would have appointed an expensive attorney to sue McPherson for his unprovoked assault on Carpenter. A working class detective would have known this and would not have assaulted a member of wealthy society in this way.

Based on IMDb Goof Guidelines, this is an unacceptable Goof for several reasons, predominately "Artistic license: Please allow for artistic license on the part of the film makers. Most movies and TV shows are not meant to perfectly reflect reality as you experience it." and "Nitpicking: It's not the viewer's job to pick apart movies and find fault with them. Allow room for artistic license."

When Lydecker recognizes McPherson's name, one can see part of the waist-band of a bathing suit worn by Lydecker in the bath tub.

The night of Laura's return, McPherson arrives at her address in a thunderstorm. As he relieves the other detective staking out the building, McPherson hands him a cigarette. The detective puts the cigarette in his mouth and walks out into the pouring rain.

When McPherson arrives to question Lydecker, he hears the fancy clock begin to chime. However, when he looks at the clock, it is seen that the hands have already advanced about two minutes.

When Lydecker gets out of his tub and puts on his robe, the seat of the robe is already wet, suggesting that this was not the first take of this scene.

The clock, which is heard to strike the time, only has one keyhole on its face. However, because the striking mechanism is separate from the timekeeping mechanism, a chiming clock must have at least two separate keyholes - one for the clock itself, and one for the strike. Presumably the prop was made only to keep the time since the production staff knew they would be adding the sound of the chime in post-production.

When Waldo tells Mark his memories of Laura, these are shown as flashbacks. However, the flashbacks include scenes Waldo couldn't have known about because he wasn't present for them, like Shelby's chats with the servant and Laura in the kitchen at the party.

Laura is supposed to have listened to all of Waldo's records of his radio shows, yet she doesn't seem to know that his discussion of great lovers of history is a recorded rebroadcast.