In a twist from the usual format, Lt. Commander Data provides the narrative for this episode, as he records a letter for Commander Bruce Maddox at the Daystrom Institute, detailing the particulars of an "ordinary day" for Data, which just happens to include the forthcoming wedding of Chief Miles O'Brien and Keiko Ishikawa, the impending birth of Lt. Juarez's baby, and the arrival of Vulcan ambassador T'Pel aboard the USS Zhukov.After turning over the bridge to Commander Riker to start the day shift, Data pays a visit to Keiko, where he learns she is unhappy and wants to call off the wedding. Being led to believe the cancellation would make Keiko happy, and knowing that Keiko's happiness is the most important thing to Miles, Data goes to Ten Forward to deliver the "good news", only to be stunned when Miles storms off. La Forge observes that it might be a good idea for Data to let him handle the delivery of such "good news" in the future.Noting the various other events on board scheduled for the day for his letter, Data heads to the transporter room to meet T'Pel, who wishes to see Captain Picard immediately. In his thoughts, Data compares his own emotional state (or lack thereof) to Vulcans in general. Upon reaching the ready room, Picard dismisses Data and Riker. Riker cooly describes T'Pel to Data as a "charming woman", and Data notes for Maddox that while he's picked up Riker's sarcasm, he's yet to master it himself.Data moves on to pay a visit to Geordi at the ship's barbershop, where Data tries calling Geordi a "lunkhead" in a friendly jest. Taken aback, Geordi advises that Data not try such ribbing on the captain. Geordi reminds Data to get a wedding gift, and he proceeds to the ship's stores, where he meets Lt. Worf. As the two decide what to give the O'Briens, Worf comments on his discomfort with human wedding rituals; as a friend, he's honored to participate in the ceremony, but he's not fond of receptions, and things like dancing. Data realizes he doesn't know how to dance, and heads off.Data arrives at sickbay, requesting Dr. Crusher's assistance as she finishes examining Lt. Juarez. Beverly is surprised when he asks her to teach him to dance, as she doesn't like to show off, and doesn't want to be known on board as "the Dancing Doctor". She agrees to help Data so long as he doesn't say anything about it. Data is paged to report to Picard, who has him research Romulan deployments along the Neutral Zone, while taking the ship to a course close to the border. He notes for Maddox that he is fortunate not to have emotional distractions in his duties, as he might be worried by such an order.Data delivers his analysis to the captain and the ambassador, reporting a confrontational policy from the Romulans that is likely to continue for the forseeable future. T'Pel rejects Picard's offer for an escort for her "mission", but Data is dismissed without discussing the details.After feeding his cat, Spot, Data is visited by Chief O'Brien, who apologizes for his earlier outburst. Data offers to make the chief more comfortable, but the progression of offers only puts O'Brien even less at ease. Miles asks Data to try to talk Keiko into reconsidering calling off the wedding. Data, deciding that Keiko may not have fully analyzed her position, agrees to give it a try. While heading to meet her, he considers that she was calm and collected earlier, suggesting her decision wasn't emotinally clouded. When he tries to point out Keiko's "errors", though, she tells him to leave her alone. Data goes to see Counselor Troi to try to make sense of the situation; Deanna suggests he stay out of it and let them resolve the matter. Troi is warmly surprised to hear that Data hopes to have his own marriage someday, and assures him he would have much to offer a partner. Before they can discuss it further, he is called away.In T'Pel's quarters, the ambassador probes Data about the ship's defenses, but when he notes that such inquiries would need to be reported to the captain, she tells him she was merely testing his security protocols, deeming them "adequate". Data notes for Maddox that he wouldn't mind having a "gut feeling" at this point to help guide him, even though he can't believe that T'Pel, as a Vulcan, might be lying.On the holodeck, Dr. Crusher is ready to give Data his dancing lesson. The only problem is that Data had recruited Beverly to teach him based on her having won a tap-dancing competition in her youth, and had neglected to tell her that this was for the wedding. When she realizes the mistake (only after an impressive tap session between the two), she proceeds to try to teach him slow-dancing, but it takes a while for Data to adjust to the complex variables of dancing with a partner. Beverly gets out of the lesson, though, when she's called to sickbay to deliver the Juarez baby, leaving Data with a holographic partner.Data next heads to the bridge, where Riker is telling a story to a female ensign at the security console, and Data notes for his letter the potential correlation between humor and sex. The joviality is interrupted when the Romulan warbird Devoras sends coordinates for a rendezvous in the Neutral Zone. T'Pel orders the Enterprise held at the coordinates until the ship is contacted by Romulan admiral Mendek, who allows the ambassador to be transported aboard. Refusing any escort, T'Pel proceeds to the transporter room, but as she beams over, the signal breaks down, killing her mid-transport.Data joins La Forge, O'Brien, and Crusher in the transporter room, where they determine that nothing is wrong with their transporter, and they detected no interference from the warbird's shields. With only a bit of molecular residue left on the pad, there isn't enough genetic material to do a full autopsy. Mendek tries to accuse Picard of arranging for the ambassador's death, implying sabotage on Starfleet's part of any attempt to normalize relations with the Romulan Empire, and calls for a retreat of both ships from the Neutral Zone. Picard assigns Data to handle the continuing investigation into the accident, and Data decides to rely on the lessons learned from studying Sherlock Holmes. He has Dr. Crusher compare the residue to the ambassador's previous transporter trace. Beverly discovers enough errors to come to two conclusions; either the ambassador suffered some unknown mutation on board the Enterprise, or the remains aren't T'Pel's.Data, La Forge, and Riker report to Picard in the ready room, where Data suggests that the only explanation for the "accident" is that while the Enterprise beamed over T'Pel, the Devoras simultaneously beamed over replicated genetic material to serve as T'Pel's "remains". Picard inquires about the position of the Devoras, which is reported to be taking a leisurly pace back home. Data notes for his letter that while Starfleet protocol is to contact Starfleet Command and wait for further orders, he believes Captain Picard isn't likely to follow that protocol - an assumption that is proven correct when Picard orders a pursuit of the Romulans.Mendak hails the Enterprise to complain about their intrusion to the Romulan side of the Zone, only for Picard to interrupt him and accuse him of kidnapping the ambassador. Even when a second warbird decloaks, Picard refuses to stand down until he has ensured the safe return of a Federation citizen. Mendek, not ready to start a war over one person, has "T'Pel" enter into view, revealing that she was a Romulan spy all along, and the admiral thanks Picard for the safe return of a Romulan citizen. But, as there are more warbirds on the way, and Mendek gives Picard one last chance to return to Federation space, which Picard quickly takes.With the ship back in friendly territory, Data seeks out Keiko to apologize for his well-meaning, but misguided, interference. She responds by telling him to get dressed for the wedding, giving him a carnation to wear as he walks Keiko down the aisle, standing in as "father of the bride". The ceremony (which includes a touch of traditional Japanese flair) goes off without a hitch, and Data's dance with the bride makes his teacher proud.After the reception, Picard visits Lt. Juarez and her baby in sickbay, noting that the miracle of life was happening just as the ship was facing almost-certain destruction. He welcomes the newest passenger aboard.Data finishes his letter with his assumption of the night watch. Worf provides a status report of ongoing ship operations and crew status. Data finishes his letter to Maddox with the conclusion that what makes people human isn't so much their biology, but their experiences, and he is optimistic that he will discover his own humanity someday.
- Bittersweet Ending: A Romulan spy who'd been masquerading as an Federation ambassador for years gets away unscathed, but Miles O'Brien and Keiko get happily married.
- Cryptic Background Reference: A throwaway line by Data that Andorian marriages consist of four people. The Star Trek Novelverse took this to mean that Andorians have four sexes, but it could just as easily mean that they practice group marriage.
- A Day in the Limelight: For Data.
- Deep Cover Agent: Subcommander Solok spent years undercover as a Vulcan and even managed to become an ambassador to the Romulans.
- Description Cut: Data figures that Keiko will react calmly to his explanation of her mistake in cancelling the wedding. She doesn't.
- Embarrassing Nickname: Beverly makes it quite clear she does not want it getting around that she was known as "The Dancing Doctor".
- Exact Words: Mendek assuring Picard that nobody is being held captive on his warbird, as the ambassador/spy wasn't abducted.
- Foreshadowing: T'Pel's reaction when she fails to get classified information from Data, which she passes off as testing his security protocols.
- Give Away the Bride: Data plays this role in giving away Keiko to Miles O'Brien at the wedding.
- Hard Work Montage: After the transporter "accident."
- I'm a Doctor, Not a Placeholder: Mott is just a barber, not a miracle worker.
- Just Testing You: Ambassador T'Pel asks Data for classified information she can't get herself from the computer due to security protocols. When Data informs her that he himself has the same protocols, she replies that she was just testing the system.
- Karma Houdini: Ambassador T'Pel, a.k.a. Subcommander Solok, gets away scot-free with being a Deep Cover Agent. Though at least the crew exposed her plan to fake her death, foiling the Romulans' attempt to end negotiations for peace.
- Know When to Fold 'Em: Picard isn't willing to risk a 5-on-1 confrontation, and orders the Enterprise back into Federation territory.Riker: Some days you get the bear, and some days the bear gets you.
- Married In Space: Miles O'Brien and Keiko.
- Transporter Accident: The Romulans make it look like a transporter accident by beaming some organic material onto the transporter pad as T'Pel is beaming away.
- The Un-Smile: Crusher tells Data to smile while dancing. He clearly hasn't mastered it.
- Vitriolic Best Buds: Data tries this with Geordi, experimenting with "friendly jibes and insults." Geordi takes it in stride, but advises him not to try it on The Captain.