Datalore: Data's EVIL TWIN shows up.
The Enterprise is cruising in the Omnicron Theta system so they can take a look at the place Data was born. Also an entire colony disappeared there. Data, meanwhile, is practicing sneezing. Right.
Riker and his party beam down to look for clues as to what happened. They return to where Data was found - a wee cave which has a secret entrance leading to a lab. There are also some child's drawings, and Dr Noonien Soong's work bench. In a storage cupboard, they find another Data-style android.
They set about assembling the other android. Picard gives a speech about humans being different types of machines. Data shows Crusher how to switch him off and she promises not to tell anyone about it. Eventually they get the android to wake up, and he announced he's called Lore, and also announces he was a replacement for Data, who was deemed imperfect.
Interaction happens. Because Lore is EVIL, he tries to give the impression of being benign but actually comes across as creepy. He tells Data that the colonists were too uncomfortable with his approximation of human mannerism, shut him down and had Soong build Data instead.
Lore reports that the colony was wiped out by the Crystalline Entity, which has possibly the crappest name of all time. Then he slips Data a mickey in his champagne and steals his clothes, revealing he was in league with the Crystalline Entity all along. Speak of the devil - the CE turns up and starts chsing the Enterprise.
Wow, Prime are really pushing Doctor Who. They've had an edvert every ad break.
The CE doesn't answer hails, probably because it hasn't got a radio set handy. Wesley expresses concerns over Data, who is, of course, Lore in disguise, and Picard is somewhat irritated that Wes would question Data.
The CE starts attacking the ship until Lore tells it to back off and asks for access to the transporters. Wesley protests some more, whereapon Picard tells him to shut up, and finally confines him to his quarters. Meanwhile, Lore beats Worf up in the lift. Wes and Crusher turn Data back on, and he goes to confront Lore.
After Lore sets Crusher on fire, Data fights with him and throws him onto the transporter, allowing Wesley to beam him into space. The Cystalline Entity retreats. Teh end.