This episode could have been subtitled "Senior Staff Goes Dumbass." Datalore is from the first season and has it's good moments, such as the introduction of Data's evil twin Lore.
It begins with an away team, including Data, on Omicron Theta, the planet where Data was first discovered by a research team 26 years prior. The Enterprise away team finds a hidden cave that was meant to look like part of the rock formations, but once unlocked, they find a laboratory and an android in parts---an android that matches Data in physical form.
They also find child drawings of people running from something that looks like a huge snowflake in the sky. This would later be relevant to the plot.
Back on board the Enterprise, a team of engineers goes to work on reassembling the android (why Data wasn't involved in this process except for using his own body as a means to which reconfigure the other android isn't explained, although he possess the intelligence to do so.) Data lets Dr. Crusher know that he has an off switch and swears her to secrecy. As he explains to Crusher, "if you had such a switch, would you not keep it secret?"
Once the duplicate is put together, then the fun begins. He introduces himself as Lore and states that Data was made first because he was an "imperfect" model.
Ok, now for the dumbass actions of the crew. Without knowing alot about the functions of this new android and what he's capable of, they go about showing him around on the bridge. Lore fakes knowing about a lot of scientific theories and mathematical equations and is found out. This should have been the first and only access to the ship he's allowed.
His lack of sincerity and telling Data not to be jealous of his abilities should have been another clue. But even Data allows him access to his computer after he expresses his ambitions and attitudes toward humans. Lore tells Data the colonists on Omicron Theta were jealous of him and forced by Dr. Soong to make a "less perfect" android (Data).
Lore writes a detailed report of his time on the colony and of the "Crystalline Entity," a being that eats all forms of life, the same one that destroyed the colony.
Chief Yar asks the captain how much they can now trust Data! Um, what about Lore, Sugarbritches? Meanwhile, Lore offers a toast of champagne to his brother Data. Data takes a sip and is rendered unconscious.
Security officer Worf notices Data is using a subspace channel. Gee, why? Maybe he's doing research, suggests Riker. In the words of Homer Simpson---"Doh!"
I know, let's have young Wesley Crusher look in on "Data" discreetly. Crusher becomes suspicious when "Data" displays the same facial tick as Lore. But that's OK, just stop imitating Lore!
"He just told me he turned him off, Mom" says Wesley when the doctor wants him to explain how Data had to turn off Lore. Um, doctor--maybe you should take that as a hint!
Now Lore is on the bridge, posing as Data. "Beautiful, ISN'T it?" says Lore as the crystal entity now appears on the viewer screen. Now Wesley knows who Data really is.
So, in short---Wesley insists it's really Lore but that's not enough to convince Riker or even the captain. They tell Wesley to "Shut up, Wesley!" They even allow "Data" to talk to the entity who is attacking the ship. Gee, Lore knew about the entity but somehow Data knows how to talk to it.
The captain becomes suspicious only after "Data" doesn't understand the phrase "Make it so."
Lore makes his way to the cargo bay area and communicates to the entity telling him the Enterprise plan of transporting a tree out to it to eat. At which time, the shields will be down and it can attack. Data, the doctor, and Wesley confront him and stop him from enacting his plan, but not before Lore gives a phaser blast to the doctor on her way out of the cargo bay when she's told to leave so he won't kill her son. Data and Lore battle it out and Lore gets thrown onto the transport pad and Wesley beams him out into space.
Thinking as the bad guy here, and considering how dumb the crew acted, why not just kill the three with the phaser and finish his plan to kill the crew using the crystal entity?
Finally, the captain asks Data, "You alright?" to which Data replies "I'M fine." Oh oh, he's not as fine as we thought. He used a contraction!
One highlight of the episode is when Worf gets his ass handed to him by Lore in the turbolift.