After the marriage of crewmembers Commander William T. Riker (JONATHAN FRAKES) and Counselor Deanna Troi (MARINA SIRTIS), Captain Jean-Luc Picard (PATRICK STEWART) and his crew of the Starship Enterprise are sent on a possible diplomatic mission to meet with Praetor Shinzon (TOM HARDY) from the Romulan Empire.
Riker and Troi's trip to her homeland has already been disrupted when Chief Engineer Geordi La Forge (LEVAR BURTON) picked up unusual signals from a nearby planet. There, they found a dismantled android, B-4 (BRENT SPINER) that appears to be a prototype for the ship's resident android, Lt. Commander Data (BRENT SPINER).
With B-4 onboard, the crew - including Lt. Commander Worf (MICHAEL DORN) and Dr. Beverly Crusher (GATES McFADDEN) -- now heads off to meet Shinzon, unaware that he's recently killed much of the Romulan Senate. Once there, they're in for a bigger surprise when they see that the leader is not a native Romulan, but rather a human who was enslaved as a boy in the Reman mines.
Now with Reman Viceroy (RON PERLMAN) at his side and Romulan Commander Donatra (DINA MEYER) unsure of his motives, Shinzon is proposing peace between their people and their longtime enemy, the Federation. Yet, Picard isn't sure of Shinzon's sincerity, a point that's only exacerbated when he willingly lets them know that he's actually a clone of Picard who initially was genetically engineered to age rapidly and replace Picard one day.
As Picard gets to look into a mirror of his younger self and wonder if he might have turned out the same way under similar circumstances, he and the crew of the Enterprise try to discern Shinzon's real motives, including what he plans on doing with a massive weapon that could easily destroy them and even Earth.