Goofs

When Picard and Data are ready to enter the Holodeck to confront Moriarty, Riker and Worf are standing beside to the door to the Holodeck. However, in the next shot, when Picard and Data approach the door, Riker and Worf are nowhere to be seen.

When Professor James Moriarty commands "arch", the arch can be seen in the back of the red chair and lamp. Shots later when Data is moving away, the arch is somehow gone.

When La Forge is theorizing on the murder victim's demise, Inspector Lestrade squats down, resting his right hand on his right knee. But in the next shot, his right arm is on his right knee.

Data states that one of Doctor Pulaski's kidnappers must be left-handed, because he is left-footed. However, this does not necessarily follow. It is perfectly possible to be left-footed and right-handed.

Moriarty hands Data a piece of paper upon which is a sketch of the Enterprise. Data immediately storms off the holodeck, and shows the paper to La Forge. As the paper was holographic, it should have vanished the moment it was removed from the holodeck. However, other episodes have established that some objects (such as food) are actually replicated within the holodeck, and thus are "real" (i.e. not holographic), depending on the needs of the program and its user (as well as the plot of the individual show).

When a murder occurs, Inspector Lestrade summons Sherlock Holmes and Dr. Watson, who are not members of the London Police, and have no business being at a crime-scene. This was a running theme of Sir Arthur Conan Doyle's Sherlock Holmes stories, and this continuing irony was the sticking point for Lestrade, who was repeatedly made to look incompetent by Holmes.

Geordi freezes the Sherlock Holmes simulation on the holodeck, yet the simulated fire in the fireplace continues to burn and flicker like normal.

Around 00:24:00 minute mark, Data and La Forge walk through Moriarty's secret door. There are chemicals on the table in round-bottom flasks. The one on the left shows a fuzzy but readable "Pyrex." The Sherlock Holmes books depicted an era up to about the year 1914. Pyrex did not become a company until 1915. However, this could be a fault of the holodeck, which may have been programmed to to generate lab glassware (from images in its databank), without being to fussy about anachronisms.

When Picard is in the conference room with senior staff members, he has his hands behind his head. This causes the fabric of his uniform to stick out unnaturally, because the male members of the main cast wore padded muscle suits to help fill out uniforms.

Series 2, episode 3. Prof. Moriarty offers the doctor "scones" which can be seen on the cake stand, complete with jam, at 32:22. At 33:50 and 37:19, the doctor tells Captain Picard that she's had "crumpets". They are very different foods.

When the thief is being held by Data, the noises his feet make reveal that he is standing on a wooden set; when he runs away however, his footsteps are added in Foley, sounding completely different.

The computer tells the senior staff that the override protocol was initiated under the authority of Lieutenant La Forge. So La Forge has the authority to shut it down, but no such attempt nor its aftermath are shown. Only Data was shown as unable to shutdown the Holodeck.

Nobody at the Bridge crew's hostage-situation meeting ever suggests the possibility of using the transporter to get Doctor Pulaski out of the Holodeck. Since a rogue AI program was commandeering the ship, this might not have worked, but it should have at least been considered.

La Forge called for the arch to request the computer to program an adversary worthy of Data, and it would be presumably at this point that the Professor Moriarty AI becomes self-aware. But he is already watching La Forge at the arch and clearly noticing the interaction, even before said command is given.

Pulaski enjoys crumpets and tea while she is Moriarty's prisoner on the holodeck. According to dialog, matter created in the holodeck cannot exist in the outside world. With that said, what happens to the undigested food in Pulaski's stomach once she leaves it?

Moriarty repeated refers to the Enterprise computer as "Mister Computer" even though it has a feminine voice. However, the character comes from the male-chauvinistic Victiorian era, where anyone with technical or scientific skills would assumed to be male.

When Geordi La Forge is looking at the picture of the Enterprise he is seeing it upside-down. He flips the picture to show Data (and the camera) and it is right-side-up. He then flips it again to look at the picture, now upside-down again.

Data, as Holmes, takes 'Whitaker's Almanack' off the shelve and returns it backwards, pages facing out, instead of the title. Data does everything as precisely as possible, so he would have put the book back correctly.

When Geordi tells Ensign Clancy he'll be gone for a while, Clancy asks where she can reach him. Data answers with the ironic "He can be reached at 221 B Baker Street". Although amusing, this is not a professional response consistent with Data's programmed precise manner of speech.

However this reply could be viewed as consistent for Data when drawing inspiration from Holmes; in the previous season's Lonely Among Us (1987) he adopted several Holmesian mannerisms, to the amusement/annoyance of the other crew members.

When discussing how Data's mind works, Data appears to be smiling to Dr. Pulaski.