Suspecting that the powerful Borg are responsible for the disappearance of an entire federation colony, Starfleet sends Lt. Commander Shelby, an ambitious young woman who specializes in Borg matters, to assist the U.S.S. Enterprise crew in their investigation. It is quickly apparent that she is interested in more than just the Borg; Riker has been offered command of his own starship and Shelby would like to replace him on the U.S.S. Enterprise. When Admiral Hanson, an ardent admirer of Shelby's, learns that Riker is planning to turn down the promotion, he suggests that Captain Picard encourage Riker to accept the position.
Meanwhile, the U.S.S. Enterprise is sent to investigate the disappearance of another starship after an encounter with the Borg. En route, the Borg intercept the U.S.S. Enterprise and threaten to destroy it unless Picard transports over to their ship. When Picard refuses, the U.S.S. Enterprise narrowly escapes the Borg's grasp and finds seclusion in a solar nebula where sensors cannot find it.
The encounter exposes a Borg weakness, which Shelby believes will allow them to destroy the ship with a burst of concentrated energy. As they plan their next move, tensions between Riker and Shelby mount when she goes above his head to Picard with a suggestion. In the heated discussion that ensues, Shelby tells Riker that he is too cautious and that he has lost his edge.
When the Borg ship begins a new offensive, the U.S.S. Enterprise is forced to leave the nebula before its retaliation system is prepared. Again in the grasp of the Borg ship, the Enterprise is invaded by three Borg who take Picard captive and return with him to their ship. The U.S.S. Enterprise then begins a high-speed pursuit of the Borg ship, as it heads for Earth.
Picard is informed by the Borg that they intend to add human biological and technical traits to theirs as part of a plan to conquer the human race, and that he has been chosen to speak for them in all communications with Earth. Back on board the U.S.S. Enterprise, Geordi informs Riker that the Borg ship must be slowed to impulse power so that the starship can divert its own power toward a shot at the kidnappers.
After initially assigning himself to lead an Away Team to the ship, Riker must grudgingly defer to Shelby when Troi reminds him that he is now in command of a ship at war. Shortly after locating Picard's belongings on the Borg ship, the Away Team begins tinkering with the ship's circuitry, causing the Borg to leave their compartments and putting the team in extreme jeopardy.
When their efforts to reach the captain prove futile, the Away Team is forced to leave Picard behind and return to the U.S.S. Enterprise. Shelby informs Riker of the situation and offers to return for the captain, but Geordi insists that they must take their shot at the ship immediately.