Troi suddenly awakens from a restless sleep to discover that she has somehow been transformed to look like a Romulan officer. Learning that she has also been transported aboard one of their warbirds, she is told by N'Vek, the vessel's Romulan Sub-Commander, that if she hopes to return to the U.S.S. Enterprise alive, she must pretend to be Major Rakal of the Tal Shiar, the Imperial Intelligence. Her instructions: to instruct the warbird commander to proceed to the Kaleb sector with a mysterious cargo. N'Vek then introduces Troi to Commander Toreth, who tries unsuccessfully to intimidate her. Undaunted, Troi orders a course for the new destination.
Back on the Enterprise, Stefan DeSeve, a Starfleet ensign who defected to the Romulans years ago, is beamed aboard after risking his life to return to Federation space. Commander Riker immediately places him under arrest for treason. DeSeve says it is urgent that he speak with Captain Picard. The ensign tells Picard that Ambassador Spock would like the Enterprise to rendezvous with a Corvallen freighter and take its cargo back to Federation territory. Unbeknownst to Picard, the rendezvous point is in the same sector where Troi has ordered the Romulan warbird.
Meanwhile, N'Vek reveals the contents of the secret cargo to Troi. Inside the containers are a high-ranking member of the Imperial Senate and his aides, being held in stasis. They are defecting to the Federation, and N'Vek is part of the Romulan underground. Major Rakal was killed in order for Troi, a Starfleet officer, to replace her. Troi continues with the impersonation, aware now that she is part of an important mission.
As planned, the warbird meets up with the Corvallen freighter. Troi senses deception from the mercenary captain of the freighter, and N'Vek suddenly destroys it, claiming that Major Rakal (Troi) ordered him to do so. A furious Toreth informs Troi that she is responsible for the deaths. Troi demands that the warbird hold position, engage its cloaking device, and wait.
At the same time, Picard is puzzled because the Enterprise does not encounter the Corvallen freighter. Picard then discovers from DeSeve that the rendezvous message did not, in fact, come from Spock, but from a member of the Romulan underground. Picard orders Data to initiate a search pattern for the missing freighter.
On the warbird, Troi chastises N'Vek for destroying the freighter so hastily. N'Vek, remorseless, instructs Troi to set their course for a Starfleet base on Draken IV. Troi follows his orders and tells Toreth to set the course. Suddenly, the warbird's sensors detect the presence of another vessel — the Enterprise. Anxious to return to her home ship, Troi threatens to eject N'Vek into space if he doesn't allow the Enterprise to track the warbird's course.
Naturally, Picard directs the Enterprise away from the warbird, and Toreth attempts to open fire. Troi orders Toreth not to, and assumes command of the warbird herself. She then communicates with Picard, asking to be beamed aboard the Enterprise. The Enterprise shields are lowered, and Troi orders N'Vek to fire disruptors at the ship. As Picard's officers react to the attack, the three Romulan defectors, still in stasis, materialize on the Bridge.
Realizing that the ineffective disrupter fire was merely a diversion to conceal the transporter beam, Toreth watches while a fellow pilot vaporizes the attacking N'Vek. Toreth attempts to hold on to Troi, but Worf activates his transporter lock on her and replaces her safely aboard the Enterprise. She is relieved to have lived through her mission, but saddened by the loss of N'Vek. Picard comforts Troi by assuring her his death was not in vain.