Original air date: December 5, 1988
Geordi La Forge and Data decide to have some fun on the Holodeck by playing the parts of Dr. Watson and Sherlock Holmes. Pulaski comes along and bets that Data can't solve a mystery where he hasn't already read the book first, like he did with all the Sherlock Holmes books.
La Forge tells the computer to create a character capable of defeating Data. Thus the character of Dr. Moriarty suddenly gains sentience (sapience), and kidnaps Dr. Pulaski. Data figures out where she's been taken and encounters Moriarty, who has learned all about the Arch command to summon the holodeck controls, and has thus learned all about the Enterprise.
Eventually Picard himself enters the Holodeck and speaks to Moriarty, who wishes to leave the confines of the Holodeck. Picard explains this is impossible; however, he promises to work on it. He saves the program, and promptly forgets about it for the next few years (until Season 6's "Ship in a Bottle").
This episode provides examples of:
- Behind the Black: When Data walks up to Geordi and asks what his assistant could have meant by stating that he's "standing beside the Invincible," Geordi points to the massive model of a sailboat that was just off frame, in full view of Data. Considering that the rest of the episode is all about Data's ability to make deductions, you'd think he would have figured it out.
- Bilingual Bonus: When he is informed that Moriarty can take control of the ship, Picard's reaction is "Merde" (French for "shit").
- Breaking the Fourth Wall: An in-universe example, as Moriarty becomes aware of the Enterprise beyond his holodeck simulation and even draws a picture of it.
- Call-Back: Data previously emulated Sherlock Holmes in the season one episode "Lonely Among Us", which is implied to be the reason Geordi set up the holodeck program for him.
- Clueless Mystery: Discussed. At first, all the holodeck does is present Holmes' actual cases or mashups of them, and Data is able to solve them instantly without any clues because he has the stories all memorized. LaForge and Pulaski argue this isn't really in the spirit of Holmesian detection. It's only after the participants ask for an original Holmes-like mystery that Data engages in actual investigation and deduction.
- Damsel in Distress: Dr. Pulaski is kidnapped by Moriarty, requiring the crew to go back inside the holodeck and rescue her.
- Eagle-Eye Detection: How Data seeks to emulate his literary hero. Unfortunately for Geordi's sense of immersion, what Data detects is the plot points from the original Holmes stories, allowing him to skip to the end.
- Exact Words: Geordi doesn't ask the holodeck to come up with a villain capable of defeating Sherlock Holmes—he asks it to create a villain capable of defeating Data. This is basically treated as the technological equivalent of a Literal Genie.
- Failsafe Failure: Geordi may be the Chief Engineer, but he is still only a lieutenant. Who the heck designed the Enterprise's computer operating system such that his administrator privileges are not only so absolute that he could accidentally lock himself out of the system, but every other officer above him in the chain of command, including Captain Picard?! It's even worse when you consider that those administrator privileges are transferred to Moriarty, who is essentially just a program written by the computer itself!
- Gone Horribly Right: The holodeck does exactly what Geordi asks it to do, just in a completely unexpected way.
- Holodeck Malfunction: As is usual whenever the holodeck decides to endanger the entire ship, they cannot just turn it off.
- Improvised Weapon: Data (as Sherlock Holmes) identifies a man's killer as his disgruntled wife, who strangled him with her necklace, pointing out that what Geordi (as Watson) took to be finger impressions on the man's throat are too evenly spaced for human fingers, but entirely consistent with the beads on the necklace.
- Innocuously Important Episode: Continuing where "11001001" started, this episode explores the idea of self-aware holographic programs, which would pave the way for other such characters like the Doctor on Star Trek: Voyager and Vic Fontaine on Star Trek: Deep Space Nine.
- Mathematician's Answer: The computer's first attempt at creating an original Holmes story is simply to slam two of the canonical storiesnote together.
- No Challenge Equals No Satisfaction: A discussed trope. Geordi is disappointed by how easily Data solves their first mystery. He and Pulaski explain that there has to be a risk of failure for any enterprise to be rewarding.
- Oh, Crap!: Data and Geordi's steadily mounting panic as they realize Moriarty has seen through the Holodeck's illusions are nothing compared to their reaction when he gives them a drawing of the Enterprise.
- Sequence Breaking: This is essentially the reason for the plot. As Data's android memory has retained the plots of all the Sherlock Holmes stories as if by heart, he ends up "solving" the mystery before the story, "A Scandal in Bohemia", has progressed far enough to give him all the clues. So, the characters decide to reprogram the simulation in such a way as to create new plot elements and an adversary capable of matching Data—in this case, a sapient Moriarty.
- Sherlock Scan: Naturally, this occurs in the Holmes simulations.
- Title Drop: When she sums up why Data can't understand the joy of solving a mystery, Dr Pulaski says, "It's elementary, dear Data."
- Wham Line: From Moriarty.Moriarty: <to himself> That dark fellow there used the word "arch" and then, I wonder... arch!
- What Measure Is a Non-Human?:
- Once again, Dr. Pulaski argues rather mercilessly that Data does not have real intelligence and is simply a machine that regurgitates facts.
- Moriarty insists on his right to exist, as he is fully self-aware and in all respects a sapient being save that he lacks a physical body.