"Unification" is a two-part episode of the syndicated American science fiction television series Star Trek: The Next Generation which features Leonard Nimoy as Spock.

Starfleet Admiral Brackett informs Captain Picard (Patrick Stewart) that Ambassador Spock (Leonard Nimoy) is missing and an intelligence scan has placed him on Romulus, raising fears that he may have defected.

Lieutenant Commander Data (Brent Spiner) discovers a visual record of Pardek from a trade conference and confirms that he is the figure seen on the intelligence scan of Spock on Romulus.

Picard calls in a favor from Chancellor Gowron (Robert O'Reilly), speaking to one of his aides and convincing him to lend them a Klingon ship that could take them to Romulus while cloaked.

Pardek has asked Spock to come to Romulus to meet with the new Proconsul of the Romulan Senate, a young idealist who has promised reforms.

Picard, Data, and Spock are soon captured by Commander Sela (Tasha Yar's daughter), who is planning a Romulan conquest of Vulcan.

Spock refuses to deceive his people by announcing the false news, even after Sela threatens to kill him, and she locks the three in her office and leaves to order the ships on their way.

By the time she returns, Data has hacked into the Romulan computer system and created a holographic simulation that distracts her long enough for the three captives to incapacitate her and her officers.

The Ambassador is intent upon his goal, realizing that it cannot be achieved through diplomacy or politics but that the Vulcan philosophy is beginning to spread among the young of Romulus.

Leonard Nimoy had previously requested $1 million to cameo in the series, but he took minimum SAG pay to reprise the role of Spock to publicize Star Trek VI: The Undiscovered Country, on which he was executive producer.

[4] This episode is one of four times that an original series character reprised his role in The Next Generation; the other three being "Encounter at Farpoint" (DeForest Kelley), "Sarek" (Mark Lenard), and "Relics" (James Doohan).

They suggested that Spock's devotion to uniting the Romulan and Vulcan people as depicted in this episode was a "metaphor for his own personal struggle".

[20] The 1995 Star Trek novel "Crossover" by Michael Jan Friedman is a story that follows up on the events in "Unification"; Spock continues to work on Vulcan, and once again Picard is involved, but also Ambassador McCoy and Scotty.