"Preemptive Strike" was the next to last episode in the series and written by Rene Echevarria and Naren Shankar and directed by Patrick Stewart.
Ro Laren returns to the Enterprise after extensive tactical training. Admiral Nechayev discusses with Captain Picard tensions between the Cardassians and a band of resistance fighters called the Maquis. The admiral wants Ro to infiltrate the group to stop their attacks because the Marquis, made up of Bajorn and other federation-friendly species, are jeopardizing a peace treaty between the Cardassians and the federation.
Ro accepts the assignment and gains the confidence of a small group of Marquis fighters when she is able to bypass the Enterprise's shields to beam over medical supplies on the shuttlecraft she and another Marquis fighter are operating. They need the medical supplies in preparation for an assault on Cardassian ships they plan to intercept that they believe are carrying biological weapons to use against them.
Ro meets with Picard to inform him of the Marquis plans and Picard hatches a trap for the Marquis by having Ro play on their suspicions of the Cardassians and lead them to an area of space where they can be captured by federation starships.
Meanwhile, Ro is developing a relationship with the Marquis fighters, one elderly man in particular who she comes to view as a father figure and had suffered at the hands of the Cardassians the way she had as a girl. As Ro and the man plan to have lunch in the compound, they are surprised by a sneak attack by three armed Cardassians and the man is killed.
Ro meets with PIcard to discuss particulars of the mission and Picard senses she has reservations about setting a trap. He tells Ro that if she's having second thoughts that he needs to know. She assures him she will carry out the mission. Picard has Riker pose as a Bajorn and relative of Ro to go on the mission with her to ensure she follows orders. But when the time comes to set the trap and everything is going according to plan, Ro points a phaser at Riker and tells him that she's changed her mind. She feels like she has finally found a place where she belongs and now has a purpose and wants to fight with the resistance. She asks to be beamed back to the compound. She tells Riker to tell the captain she is sorry. Riker returns to the Enterprise to give the captain his report. Picard is dismayed at the turn of events and of Ro's betrayal.
I liked this episode because it shows that sometimes military training doesn't ensure a person will follow orders, orders that may conflict with their conscience and convictions. As a child, Ro had seen her father tortured and killed by Cardassians and believed that they were planning assaults on Bojorn civilians and came to resent the federations' alliance with the Cardassians, especially after the surprise attack.
I think too that the episode doesn't wrap things up neatly into a black or white scenario, but leaves the audience thinking who is right and who is wrong and there is no clear-cut answer. This more closely resembles the reality of conflicts between factions.