• Jean Luc Picard: Patrick Stewart
• William Thomas Riker: Jonathan Frakes
• Data: Brent Spiner
• Geordi Laforge: Levar Burton
• Worf: Michael Dorn
• Beverly Crusher: Gates McFadden
• Dianna Troi: Marina Sirtis
• James T. Kirk: William Shatner
• Tolian Soran: Malcolm McDowell
• Guinan: Whoopi Goldberg

A holodeck celebration of Worf's promotion to lieutenant commander is cut short by a personal communique to Picard and a distress call from the Amargosa Solar Observatory. By the time the Enterprise reaches the observatory, attackers - apparently Romulans - have already left their mark. Back on the Enterprise, Data decides that the time has finally come for him to try Dr. Soong's emotion chip for himself. Dr. Soran, a researcher from the observatory, insists on returning there so he can continue his work in spite of the recent attack. It is discovered that the Romulan attackers were searching for trilithium, a vital component in a new and highly destructive explosive device. Data and Geordi are scanning for trilithium on the observatory when Data is overcome with emotions; Dr. Soran appears and takes this opportunity to take them hostage. Aboard the Enterprise, Picard reveals to Troi that he received a message earlier informing him of the death of the only other living members of the Picard family, leaving him the sole survivor of his family line. When Soran launches a probe from the observatory into a nearby star, the star explodes, leaving only minutes or seconds before the stellar shock waves reach and destroy the Enterprise and the entire solar system. Worf and Riker beam to the observatory and rescue the fear-stricken Data, but Soran keeps Geordi in his sights, transporting away to a Klingon Bird of Prey which, along with the Enterprise, barely escapes the star's death throes in time. The Klingon ship is commanded by the Duras sisters.

On the Enterprise, the incident nearly 80 years ago involving the Enterprise-B is investigated when Soran and Guinan are both discovered to have been there. Guinan explains to Picard that Soran is trying to replicate the ribbon of immense energy that destroyed the ship they were on decades ago, since it was a doorway to an ethereal plane of eternal happiness, so he can return there. Picard and Data find out that Soran destroyed the star to divert the energy so he can once again reach the Nexus, but another star will have to be detonated before Soran can reach his goal - and that star's solar system is heavily populated. The Enterprise tracks down the Duras sisters' ship, and Picard agrees to exchange himself for Geordi as a hostage so he can try to stop Soran. Picard finds himself on one of the target star's planets, where Soran is moments away from firing another probe that will finally allow him to reach the Nexus. Geordi is returned to the Enterprise with an undetectable transmitter that sends his VISOR's input to the Klingon sisters, who use information Geordi sees in engineering to launch a withering attack on the Enterprise. Worf discovers a weakness in the Bird of Prey's defenses, and manages to destroy the Duras sisters at last, but the Enterprise has sustained more damage than can be contained, and the crew is evacuated to the saucer section so the warp drive section can be jettisoned before it goes critical.

Picard manages to attack Soran, but not before the scientist launches his probe into the star. The Enterprise's drive section explodes, catapulting the saucer straight into the planet's atmosphere, where it lands safely, though the Enterprise will never take to the stars again. When the Nexus opens up, Soran and Picard are sucked into it; moments later, the exploding star destroys the planet the Enterprise's saucer has landed on.

In the Nexus, Picard encounters a fragment of Guinan that was left in the rift in the Enterprise-B incident. She informs him that he can go to whatever time he wishes, and Picard intends to use this ability to prevent Soran from launching the probe that destroys the Enterprise's crew. Guinan also suggests that Picard seek the help of another starship captain who was captured in the Nexus when the Enteprise-B was struck by its energy discharge after rescuing Guinan. That individual happens to be James T. Kirk. Picard convinces Kirk to help him stop Soran, and they emerge at the point in time before Soran launched his final probe. Kirk battles Soran as Picard tries to sabotage the probe, but Soran manages to shoot Kirk and the probe is launched anyway. However, Picard's efforts send the probe back into the planet harmlessly, and the Nexus cannot be reached. When Soran assaults Picard in a blind fury, Picard is left with no choice but to kill him. Captain Kirk dies just before a shuttle from the Enterprise arrives to retrieve Picard, while the Enterprise crew is evacuated to the starship Farragut, leaving the wreckage of Picard's most legendary command on the planet surface.