"Undertow" - Nella Daren ("Lessons") returns to the Enterprise as an adviser who is evaluating a species applying for admission to the Federation. Riker notices errors and oversights in her work. Picard is inclined to give Daren the benefit of the doubt. At the same time, Starfleet Medical contacts Dr. Crusher to inform her that Daren has stopped taking her antipsychotic medication, which is a mandatory condition for her to be on active duty. Crusher determines that the sensitive nature of Daren's duty warrants breaking medical confidence to the captain. This settles the issue with Picard, who immediately orders Worf to accompany him to relieve Daren.
When Picard and Worf arrive in the interview room where Daren and her assistant are meeting with planetary bigwigs, Daren senses that they are there to relieve her because security is present. She draws her own phaser-1 and takes everyone hostage. She forces Worf to withdraw, leaving her assistant, Picard, and two planetary bigwigs in the room.
Outside the room, Crusher informs Riker that, after reading Daren's medical records, she believes that Daren never recovered from the rescue mission on Bersallis III. Daren had a psychotic break. She responded to treatment, but it seems that she was less well than even her therapists had determined. Given the risks, Riker decides that Picard must know this, so he tells Picard over his communicator. Everyone in the room hears this. Daren responds by saying that she wants the new species not to join the Federation, because she believes that Starfleet is a corrupt organization that considers its officers expendable.
Outside the room, Riker and Worf can do nothing. Daren has set her phaser to maximum. Even if they try to beam her out, there is a risk of a lethal discharge from the phaser that could kill everyone else in the room, and an even greater likelihood of increasing the severity of the diplomatic incident already in progress.
A member of the species arrives who says they are friends with Daren. The alien government has granted permission for him to enter the room to negotiate. Riker has little choice but to agree. The alien takes Daren's mind back to a time when they admired a concert performance. Daren reminisces, but then she realizes that it is a false memory. She tries to fire the phaser, but she can no longer move her hand; it is completely crystalized. O'Brien transports her out of the room and deactivates her phaser. Crusher cannot save her hand, but she believes a new one could be grown. Daren is sedated and on her way to recuperate.
The alien used telepathy to distract Daren while neutralizing her ability to use the weapon. Worf is impressed and believes that they will make a fine addition to the Federation. Picard isn't so sure, but he leaves Daren's subordinate in charge of further evaluation. Two Starfleet vessels arrive, one to relieve the Enterprise in the diplomatic mission, another to take Daren away.
The only counsel Picard has is from Troi. When Daren arrived, Troi could sense nothing amiss in Daren's emotional state, because she was still taking her medication at that time. Clearly, she was deeply wounded, more deeply than Troi could read, and it was in no way Picard's fault. Daren isolated herself from Picard. This is Troi's advice. Picard does not accept that and considers whether he should accompany Daren to the rehabilitation colony, to try to reach her. Troi says that it's more likely to cause additional problems, as he is intimately involved in the events that drove her mad in the first place. Troi thinks that the colony Daren is going to is a good one. Obviously, Daren fell through the institutional cracks, and Troi assures Picard that these will be assessed. Dr. Crusher has already relayed to her that there will be no easy fixes. For now, they can only mourn the loss of an additional casualty from the rescue at Bersallis III, but at least there is hope that this one will eventually recover.
Next - "Room Inside"