On Romulus, members of the Romulan Senate debate terms of peace and alliance from the Reman rebel leader Shinzon. The Remans are a slave race of the Romulan Empire from the neighboring planet Remus, used as miners and cannon fodder. While a faction of the military supports Shinzon, the Praetor and Senate are opposed to an alliance. After rejecting the motion, the Praetor and senators are disintegrated by a device left in the room.
Meanwhile, the crew of the Starship Enterprise prepare to bid farewell to newly-married officers William Riker and Deanna Troi. The android officer Data serenades the couple with a rendition of “Blue Skies” at a reception. En route to the ceremony, they discover an energy reading on the planet Kolarus III near the Romulan Neutral Zone. Captain Jean-Luc Picard, security officer Worf, and Data land on the planet and discover the remnants of an android resembling Data, named B-4. The trio are attacked by the native population, and leave the planet with B-4, which they deduce to be an earlier version of Data.
Enterprise is ordered on a diplomatic mission to Romulus, where Shinzon has taken over the Empire and professes a desire for peace with the Federation. On arrival, they learn Shinzon is a clone of Picard, secretly created by the Romulans to plant a high-ranking spy into the Federation. The project was abandoned when Shinzon was still a child, and he was left on Remus to die as a slave. After many years, Shinzon became a leader of the Remans, and constructed a heavily armed flagship, Scimitar. The Enterprise crew discover that Scimitar is producing low levels of deadly thalaron radiation. There are also unexpected attempts to communicate with the Enterprise computers, and Shinzon invades Troi’s mind through the telepathy of his Reman viceroy.
Doctor Beverly Crusher discovers that Shinzon is aging rapidly because of the process used to clone him, and the only possible treatment is a transfusion of Picard’s blood. Shinzon kidnaps Picard and B-4, having planted the android on Kolarus as a lure. Data reveals he swapped places with B-4, and rescues Picard. They determine Shinzon plans to use Scimitar to invade the Federation, using its thalaron radiation generator to eradicate all life on Earth.
Enterprise races back to Federation space, but is ambushed by Scimitar. Despite the aid of two Romulan Warbirds, Enterprise is heavily damaged. Picard rams his ship into Scimitar, crippling both vessels. Shinzon activates the thalaron weapon in an act of mutually assured destruction. Picard boards Scimitar alone to face Shinzon, and kills him by impaling him on a metal strut. With Enterprise’s transporters damaged, Data leaps the distance between the two ships equipped with an emergency transporter, beaming Picard off the ship, and sacrifices himself to destroy the thalaron generator and Scimitar with it. The crew mourn Data, and the surviving Romulan commander, Donatra, offers them her gratitude for saving the Empire.
Back at Earth, Picard bids farewell to Riker, who is leaving to command the USS Titan. Picard meets with B-4, and discovers that, before he boarded the Scimitar, Data downloaded his memories into B-4, allowing him to live on. As B-4 starts singing “Blue Skies”, Picard leaves B-4’s quarters and smiles.
Star Trek Command 