Ro Laren's "homecoming" is interrupted when Federation ships from the renegade group the Maquis attack a Cardassian vessel near the Demilitarized Zone. The U.S.S. Enterprise crew is able to successfully chase away the vigilantes. However, the Cardassians, led by Gul Evek, are angered by the growing threat posed by the Maquis, and promises Cardassia will take matters into its own hands if the Federation does not force the Maquis to uphold the peace treaty. Admiral Nechayev decides to send Ro Laren into the Maquis community as an undercover operative. Ro is uncomfortable with the assignment since, as a Bajoran, she has spent most of her life fighting the Cardassians, but accepts the mission out of loyalty to Picard.

Ro begins her deception in an alien bar, pretending to be a fugitive accused of killing a Cardassian, and talks with a man named Santos, who stuns her with a phaser. Upon awakening in a Maquis settlement, Ro tells the group who surrounds her that she sympathizes with their cause. The Maquis members check her story and, when they find it to be true, allow her to join the group. Ro soon bonds with an older man named Macias, who takes her under his wing. Later, Ro learns that the Maquis suspect the Cardassians are smuggling biogenic weapons into the Zone. In order to launch a preemptive strike, the group will need extra medical supplies, but has none on hand. Seizing this chance to convince the Maquis of her loyalty, Ro takes along a skeptical member of the group, Kalita, in order to raid the Enterprise for the needed supplies. During the attempt, Picard realizes what Ro is doing and plays along, and as a result, Ro successfully convinces the Maquis that she is truly on the group's side.

Afterward, Ro meets secretly with Picard and tells him about the Maquis' suspicions. Picard sees this as the perfect opportunity to set a trap and lure the entire group into attacking a false target. However, he senses that Ro is growing increasingly uncomfortable with her mission, but she assures him that she will do her duty. She then returns to the colony and starts planting the misinformation needed to lure the Maquis. However, her guilt continues to grow, especially when the group is attacked by a trio of disguised Cardassians. Macias is killed in the attack, and tells Ro with his dying breath that she must take his place in the fight.

Ro meets again with Picard and tries unsuccessfully to lie to him about the Maquis' plans. Unsure of her commitment, Picard has Riker accompany her, posing as her brother. As the Maquis head for the border, the Enterprise waits to ambush the group. But at the last moment, Ro grabs a phaser, points it at Riker, then reveals the Enterprise's location. The Maquis ships retreat, and Ro goes with them, asking Riker to tell Picard she is sorry she let him down.