En route to a vacation and seminar on Risa, Geordi La Forge is kidnapped by the Romulans and subjected to days of brainwashing. While a double is sent to replace him at the conference, Geordi is forced to endure a painful series of mind-altering experiences designed to put him under complete Romulan control.

Meanwhile, the U.S.S. Enterprise is assigned to escort Klingon Ambassador Kell to the Kriosian system, where one of the Klingon colonies is fighting for independence. The governor of Krios, Vagh, charges that the Federation is secretly aiding the rebels. Though Picard denies the accusation, Vagh produces weapons seized from the rebels which appear to be Federation issue.

When Geordi returns he has no recollection of his ordeal, having been planted with false memories of a relaxing vacation on Risa. Shortly after his arrival, however, Data detects the presence of intermittent E-band emissions commonly associated with Romulan transmissions. Data tries to pinpoint the source of the emissions, and also works with Geordi to analyze the rebel weapons. The two quickly realize the rifles were manufactured by the Romulans to look like Federation guns.

Picard hypothesizes that the Romulans are plotting to drive the Federation and the Klingon Empire apart, which allays some of Vagh's fears. However, a short time later an outraged Vagh contacts Picard and informs him the Klingons have intercepted a shipment of weapons headed for Krios, which originated from the U.S.S. Enterprise. Data's examination confirms an unauthorized transport was sent from a cargo bay, but the memory chips in the computer were erased to hide the perpetrator's identity.

As Picard begins an investigation, Klingon warships uncloak and surround the U.S.S. Enterprise. Ambassador Kell offers to go to Krios and invite Vagh to witness the investigation, ostensibly to convince him of the Federation's good faith. But shortly before Kell leaves, he summons Geordi to his quarters, where it immediately becomes apparent that Geordi is under his influence without knowing it. Kell, who programmed Geordi to transport the weapons, commands him to kill Vagh when they return from the planet and claim he acted on behalf of Starfleet.

Kell's transmission to Geordi produces another E-band emission, which Data is able to trace to Kell. Data quickly deduces what is going on and is able to stop Geordi just as he is making his assassination attempt. Kell is exposed as a traitor conspiring with the Romulans, and he is placed in Vagh's Custody. With war averted, Troi begins the arduous task of deprogramming Geordi, who has no recollection of what has happened and is unaware of his participation.