The Enterprise-D responds to a distress call from New Providence colony, only to discover a crater where the colony was, similar to several other colonies along the Romulan Neutral Zone and the planet in System J-25. Lt. Commander Shelby, a tactician and expert on the Borg, arrives to assist the Enterprise crew in determining the cause of the colony's disappearance. However, it quickly becomes clear that Shelby is looking to become second-in-command of the Enterprise, as Commander Riker is being pressured to take command of his own ship against his will by Starfleet. With Shelby's help, they confirm the colony was assimilated by the Borg; after receiving word of a Borg Cube sighted in Federation space, the Enterprise leaves to meet it.
When they catch up with the Cube, the Borg demand the Enterprise turn over Captain Picard. The Borg lock the Enterprise in a tractor beam and attempt to cut open the ship upon Picard's refusal. Shelby suggest a means of altering the frequency of the ship's phasers to bypass the Borg defenses, allowing them to destroy the tractor beam and escaping to a nearby nebula to effect repairs and determine a strategy. Using Shelby's previous tactic, they work at modifying the Enterprise's deflector dish in the same manner as the phasers, which will be destructive to the Cube should they weaken its defenses. Before repairs are completed, the Borg flush the Enterprise from the nebula with magnetometric-guided charges, and then board the ship in its weakened state, abducting Picard. The Borg Cube moves off at high warp speed towards Earth, with the Enterprise giving chase.
Riker, now in command of the ship, prepares to join an away team to transport to the Cube to rescue Picard, but Troi reminds him his place is now on the bridge, and Commander Shelby leads the away team. Aboard the Cube, the Borg are unresponsive to their presence, allowing them to locate Picard's discarded clothes. With the Enterprise nearly at the point where they will no longer be able to keep up with the Cube, the away team destroys power nodes inside the Cube, forcing it out of warp but also alerting the Borg drones to their presence. As they prepare to transport out of the ship, they spot Picard, now assimilated as a Borg drone. Once aboard the Enterprise, the Borg contact the ship, with Picard speaking for the Borg. He tells the Enterprise that he is now "Locutus of Borg", and to prepare for assimilation. Riker, after confirming the deflector dish is ready, gives the order to fire.