Goofs

On the list of jewelry owners, the room number of Mrs. Jessie Stevens is given as 541, but when John Robie accompanies Mrs. Stevens and her daughter to their rooms, the numbers on their doors are 625 and 623, respectively.

When Robie and Hughson are walking at the flower market, they look back at a few men following them. As they do, a woman in a bright pink dress is walking towards the two men behind them, but as they turn back, the same woman (who should have been behind them) is walking towards Robie and Hughson.

After Robie leaves Danielle's boat and swims to the beach, he lies down in the sand. Since his body is all wet, a lot of sand sticks to it. Yet in the next shot when he is asked to answer the phone at the beach, there is no more sand on his body.

(at around 9 mins) An overhead shot (from a helicopter) shows the police chasing and catching the car driven by Germaine the maid, who must stop for some sheep. To her left is a hill, and the police stop to her right. Cutting to ground level, the hill behind her is not seen, instead there is a more distant background.

When John leaves the car to retrieve the picnic basket from the trunk, he slams the door shut, but when he returns the door is open and he sits down in the opening.

In the roulette scene a double zero "American" wheel is used with a single zero "European" layout. They are not mixed in real life.

John says he'll leave his clothes with Danielle, but later, when he is at the flower market, he's in the same clothes.

However it is quite likely that he met up with her before going to the market and this meeting was simply omitted as it contributes nothing else to the story. This is the only plausible explanation, since he was unlikely to be concealing money in his swimming trunks either, and it's improbable that he walked the 20 miles from Cannes to Nice for the meeting, barefoot in just his trunks.

(at around 4 mins) Five policemen arrive at Robie's house in one car and ask him to accompany them back to the station for questioning. However, there would have been no room for Robie in the car with the five policemen, they would have needed a second car.

This might have been intentional by the police; they could use it as an excuse to leave one of their men behind saying they'd send a car back for him. Thus, the officer would be able to search the house for the stolen jewels.

The note with the warning message on Carlton Hotel stationary that John Robie receives at the hotel's front desk before going to the Beach with Francie has the impression of a similar message on it, made when the prop department was creating various notes for the director to select for use in this scene.

When John and Frances first arrive for their "picnic" and John is standing at the back of the car, his shadow can be seen on the backdrop of the canvas, a flat shadow, which would not be possible in the natural conditions which the canvas depicts.

For the first 20 minutes or so, Cary Grant (as John Robie) is wearing a red cravat with white polka dots. At about the 18-minute mark, Robie jumps in a boat driven by Danielle to escape the police. In several angles on the boat, his cravat is solid red, and then he goes below deck to avoid being seen by a helicopter. There is one shot below deck, probably a later re-shoot, where Robie is not wearing a cravat at all. However, after putting ashore, he is wearing the red-and -white polka dot cravat again.

When driving, John and Frances lean the wrong way when Frances turns the wheel. So do the cops chasing them.

When our heroes watch the fireworks display from a hotel room, no light from the fireworks is reflected on any of the surfaces in the actual hotel room, despite the fact that it is a massive light display and they are watching it in the dark (because it's just a rear projection).

Near the start when Robie is talking to Bertani in the restaurant, just before he tells him about Hughson, Bertani speaks, but his lips don't move.

When driving from the villa, before the picnic, the reflections of the studio lights can be seen on the car.

In the initial chase scene, the maid travels west past Gourdon, then is seen going east past Tourettes-sur-loup. That trip from the villa in Sainte Jeanette would take half a day. The same issue occurs when Robie and Francie go to inspect villas. They travel from the Carlton to upper Cannes, then all the way past Eze, and then back toward Monaco. Good luck doing that in such a short time.

While eating lunch at Robie's villa, when Hughson gives Robie the list of a half-dozen people with jewels worth being stolen - with details and habits included - it is one sheet of paper. Robie unfolds the sheet, and only one name and pertinent information is included (Jessie Stevens). Then, Robie goes touring the houses of other people on the list, but their information was never included on the actual list Hughson gave him.