Star Trek: The Next Generation - Unification(2013)

Captain Picard embarks on a secret mission to find Ambassador Spock, who is rumored to have defected to the Romulan Empire. Picard and Data, with the help of a cloaked Klingon ship, travel to Romulus to uncover Spock's actions. They discover that Spock is not a defector but is instead working with an underground movement to foster peace and unification between the Vulcan and Romulan peoples.