Revealing mistake: When the band in the nightclub performs the made up song "Mr. Music Man", the suave Mr. Stone, the musician Miss Fisher ends up dancing with, is doing one heck of an hilariously incompetent job at faking to play an instrument, basically playing air-banjo strumming about 3 inches above where the chords are, and wildly off tempo. In the closing bit of the song (as the singer sings "To sin") he even moves his hand at the side of the strings and not above them. (00:03:30)
Continuity mistake: When Miss Fisher is watching Charles argue with the future victim who grabs him by the lapel, she holds her drink from the top or at the bottom of the glass depending on the angle. (00:03:40)
Continuity mistake: As the police arrives on the crime scene, the body is lying with both arms spread on the floor. When Jack kneels by it for the examination, the dead man has one hand to his chest. (00:05:35)
Continuity mistake: In the scene with the chicken on the kitchen table, the chicken stands in different spots in the different shots. Also, it took a dump on the newspaper in between the first shot and the rest. (00:13:55)
Continuity mistake: When the two blokes who help Miss Fisher are playing darts, the close-up shows the dart sticking really close to the left line of the segment. When Miss Fisher is nearly impaled by Bert's off-target projectile, the dart on the board is better centered. (00:15:25)
Character mistake: Miss Fisher is shown tumbling her way into Leonard's apartment in a less than graceful manner, with a rather audible thump, and rolling on the floor and to her feet making quite a ruckus. Despite that, Bobby, who is presumed to be alert and on edge since he's breaking and entering, is completely oblivious of her presence. (00:16:30)
Factual error: When the compromising pictures of the lovers in bed are shown, it's also shown that some are taken in rapid succession, with Charles noticing, covering up, charging at the camera. All this quickfire shutter action would be really too much advanced paparazzi tech for the 20s! In the same episode Miss Fisher gets her mugshot taken and it's taken with a big and clunky camera. (00:20:00)
Factual error: At the police station, as Miss Fisher hands the food basket to Jack to walk away with Dot, a wall calendar indicating the episode as taking place on August 11, Thursday. The established year is 1928, so it should be a Saturday. (00:22:30)
Continuity mistake: Outside Mrs. Freeman's house, Miss Fisher is putting her gloves on. She puts on just the left glove, but walks to the car wearing a right glove and again has to put on the left one. (00:25:50)
Audio problem: When Miss Fisher is interrogating Stone and asks him "What's the matter Mr. Stone..." he's gulping down his liquor. She finishes the sentence ("cat got your tongue?") in a separate shot, and the sound of him just putting down the glass is heard. But if you look at the little bit of him that is poking in the foreground, he's puffing smoke instead. Kinda hard to do that with a mouthful of whiskey. (00:31:40)
Continuity mistake: During the interrogation of Mr. Rogers, the distance between the trumpet and the mute constantly changes between shots. And when he says "So what? Doesn't prove a thing!", Miss Fisher is holding her hand on top of the mute, instead of having her arms folded. (00:49:40 - 00:51:00)
Plot hole: The murder weapon during Miss Fisher's demonstration hardly appears to generate enough momentum not just to send a projectile across the room with lethal force, but also do it achieving full penetration through clothes, disappearing entirely inside the body so the coroner wouldn't notice. That's assuming that the coroner did not even bother to in fact open up the cadaver and perform autopsy, which would be strange, especially with a weapon of undisclosed characteristics, when finding out more about the depth and damage to internal organs would have been crucial. And with any autopsy the dart would have been found, solving the case almost immediately. (00:49:45)
Plot hole: Talking about the murder weapon, the coroner says that the wound was a "horizontal" stab. Nerine's confession is ruled out because she mimics the attack at an angle. Funnily enough though, during interrogation, Jack himself makes a remark about the stage being a spot overseeing the room, and the killer was in fact on stage, and standing. When we see briefly the flashback of the murder, it's clear that the trumpet is way above the head of everyone dancing. So the projectile wound would hardly be "horizontal."
Factual error: At the beginning, Charles is trying to sell his airplane to Miss Fisher: he calls it a "Tiger Moth." The series is set in the 20s, and he should have simply said a "de Havilland Moth", which were the most popular recreational aircraft of the decade. The Tiger Moth though came out in 1931, making its mention an impossibility. (when we see the plane, it's a model manufactured in 1942, going by its registration number).
Answer: Louisa's watch was broken during the struggle to get away from her attacker.
Bishop73