The Borg take Picard and the Enterprise must defend Earth.
The Borg destroy a Federation colony on Jouret IV, and Starfleet sends Lieutenant Commander Shelby, an expert on the Borg, to join the Enterprise. Shelby is ambitious and openly wants Riker's job, while Riker himself is deciding whether to accept command of the USS Melbourne.
The Enterprise confronts a Borg cube, and Borg drones beam onto the bridge and abduct Picard. An away team led by Shelby boards the cube but fails to rescue him.
The Borg assimilate Picard and turn him into Locutus, their voice to humanity. As the episode ends, Riker, now in command, orders an untested weapon fired on the cube, though Picard is aboard. This was the first season-ending cliffhanger in the series.