The Enterprise crew finds a disassembled android identical to Data at the site of the Omicron Theta colony—where Data was found—which was destroyed by a life form dubbed "the Crystalline Entity." The reassembled android, Lore, claims that Data was created first, and was considered the "less perfect" android. Lore is given a tour of the Enterprise, and later on he tricks Data into drinking something that immobilizes him. He then switches clothes with him, copies over his Facial Tic over to Data and erases his own, and pretends to be Data, claiming that "Lore" attacked him in his quarters. All this is for the purpose of offering the Enterprise to the Crystalline Entity, which he had been in contact with and invited to Omicron Theta in the first place, gaining its gratitude for all the life forms it consumed there.
Wesley Crusher is suspicious of "Data" (Lore), but is brushed off by the senior officers when he voices his concerns. He goes to Data's quarters and finds Data unconscious, and gets his mother, Dr. Crusher, to revive him.
The ship encounters the Crystalline Entity, and the ship's shields protect it from the feeding beam, but Lore has a plan to trick Picard into dropping the shields, offering to replicate a large tree and beam it out into space, then destroy it with phasers to demonstrate the Enterprise's power. He goes to the cargo bay and has a showdown with Data, who manages to get Lore onto a transporter pad so Wesley can beam Lore out. If beaming a tree into space and destroying it would result in dropping the shields enough for the entity to attack, then why doesn't beaming Lore into space have the same effect? This is never answered. Finally, Data is asked how he is handling the circumstances. Data says "I'm fine."
Tropes in this episode include:
- Absentee Actor: Troi does not appear. Unlike in "Hide and Q", no explanation for her absence is given.
- Apocalyptic Log: The crew find drawings from the children of the colonists. Each has a giant snowflake in the sky, and horrified people trying to run from it.
- Cassandra Truth: Wesley has an excuse for acting like an insufferable teenager in this episode, since he repeatedly told everyone his suspicions about Data but nobody listened! What makes it unforgivable is that they actually told him to check on Data in the first place!
- Double Vision: Allowing Brent Spiner to play both Data and Lore, and including impressive split-screen effects so that his face can be seen on both characters at once.
- Early Installment Weirdness: Upon detecting the Crystalline Entity, there's this very out-of-place line:Geordi: Captain, I'm picking up a bogey coming in on a five o'clock tangent.
- Evil Twin: The introduction of Lore.
- For the Evulz: It's very unclear what exactly Lore gets out of his alliance with the Crystalline Entity that made him betray the colony in the first place.
- Groin Attack: Lore does this to Worf.
- Hypocritical Humor: After Picard says "Shut up, Wesley!", Dr. Crusher is critical of Picard, but when Wesley tries to speak up again, she says "Shut up, Wesley!" herself.
- Idiot Ball: Riker grabbed it quick to dismiss the possibility of Lore impersonating Data.
- "It" Is Dehumanizing: Data calls Picard out on this.
- Mama Bear: When Lore threatens Wesley, Dr. Crusher shows how much she looks like she means business with a phaser.
- Meaningful Name: Contrast the name "Data" meaning "facts, statistics, or items of information" with "Lore" meaning "the body of knowledge, especially of a traditional, anecdotal, or popular nature, on a particular subject." The two are similar but data implies pure information and is dispassionate, while lore is less precise.
- No-Sell: Worf finds out the hard way that Lore is impervious to his attacks.
- Not Now, Kiddo: Wesley tries to tell Picard that's something's amiss about Data when Picard tells him to shut up.
- Prepare to Die:Lore: [to Wesley] Are you prepared for the kind of death you've earned, little man?
- Retcon: It was only with this episode that the production crew came up with the idea that Data never used contractions as a way to tell him apart from Lore, despite him having used them in earlier episodes (and even at the end of this one, thanks to a flub by Spiner).
- Shibboleth: Data can't use contractions, Lore can. Although this failed spectacularly because Data is heard using a contraction right at the end! Fans fond of growing Epileptic Trees were briefly convinced that this meant Lore actually had somehow replaced or taken over Data, rather than just being a mistake. Considering there was no way they could have missed the flub (since it's a plot point) one wonder why they didn't just treat it like any other blooper and reshoot it.
- Thrown Out the Airlock: Lore is beamed away and left floating in space. It's later revealed he spent two years like this, until being picked up by the Pakleds.
- The Unapologetic: Picard and Riker never do apologize for being so dismissive of Wesley
- The Worf Effect: Lore easily kicks Worf's ass in the turbolift.
- Uncanny Valley: A (supposed) in-universe example with Lore, who claims that he was deactivated because the Omicron Theta colonists found him too unsettling to live with. That said, given Lore's general behavior it's possible that he's being an Unreliable Narrator, and that he was actually deactivated for being a complete psychopath.
- Undying Loyalty: Data assures Picard that while Lore is his brother, his loyalty is to the Captain and Starfleet.