When the Enterprise arrives, a menacing-looking alien vessel of an unknown design is found in orbit around the planet. Efforts to communicate with it yield nothing, so Riker, Worf and Data transport to the surface, finding only dead bodies in the science station. Then, Data opens a door to encounter ... one of the Borg. Several more of the warrior aliens charge in, attacking the officers, while in space the strange vessel suddenly fires on the Enterprise. However, the Borg on the surface are not performing as the calm, mindless drones encountered in previous battles, but are instead quick, vicious — ready to kill instead of assimilate ... and are behaving like individuals. They focus on Data, surprisingly identify him by name, then quickly rush him. The emotionless android becomes enraged, slams a Borg against the wall, and violently beats him to death. The other Borg abruptly disappear, then the alien vessel moves away and travels into a blinding flash of light, vanishing. Riker and Worf stare at Data, who realizes the impossible — he got angry.

In the Holodeck, Data recreates his fight with the Borg, but cannot recapture the anger. He returns to duty as they go to Red Alert — the Borg are attacking the MS 1 Colony. Curious, Picard wonders why the Enterprise in both cases happened to be the nearest ship to these conflicts. They encounter the same alien vessel, which escapes again into the flash of light — but this time, the Enterprise gets drawn into the strange subspace distortion with it.

Returning to normal space, the alien vessel immediately fires upon the Enterprise. Two Borg materialize onto the Bridge, but Worf quickly kills one attacker and wounds the other. After the fight ends, they realize the Borg ship has once again vanished. Placed in the Brig, the survivor tells Picard he is called Crosis, a name given to him by an entity called the One. Data is left alone with Crosis, who tells the android he is perfect for assimilation. While talking, Crosis surreptitiously touches a control on his artificial arm, and Data's head tilts very subtly in response. Crosis reminds Data about the pleasure he felt killing the Borg on Ohniaka III, and slowly convinces Data that it is worth anything to feel an emotion again — even if it means killing his friend Geordi. Abruptly, a shuttlecraft leaves the Enterprise, emitting a tachyon pulse that causes the subspace distortion to appear. The shuttlecraft and the light then vanish. The passengers: Crosis and Data.

Geordi duplicates the tachyon pulse, and the Enterprise travels through one of the subspace conduits, exiting 65 light-years from where they were. The shuttlecraft's energy trail is traced to an unexplored planet. Riker, Worf, and a heavily-armed away team transport down and find the shuttlecraft, now abandoned.

Picard institutes a massive search for Data, utilizing all available personnel, including himself, and leaves Dr. Crusher in command of the Enterprise. Picard's team, composed of Geordi, Troi and a security guard, search for hours, then discover a large alien building. They enter a huge, empty, foreboding room that seems to be some kind of meeting hall, and realize it could be a trap, but before they can escape, huge groups of Borg run in from everywhere, screaming incessantly and trapping the away team. The security guard tries to fire, but the surrounding Borg kill him on the spot. They close in on Picard, Geordi and Troi, who prepare to face certain death, when a voice commands the Borg to stop. The three officers turn toward the voice and are stunned to see Lore, Data's "brother."