When Data receives strange energy readings from Alpha Onias III, an uninhabited planet near the Neutral Zone, Picard suspects the Romulans and sends an Away Team led by Riker to investigate. On Alpha Onias III, communications with the U.S.S. Enterprise break down and the mission is aborted. Later, Riker awakens in sickbay to a graying Dr. Crusher, who tells him that he is recovering from a retroactive virus he contracted during the mission 16 years ago — a virus that only recently became active and destroyed all of his memory from the moment he was infected. Riker learns that he has been Captain of the U.S.S. Enterprise for nine years and has a son, by a wife who has been dead for two years. But his most shocking discovery is that he is about to lead negotiations for a peace treaty between the Federation and their long-time adversaries, the Romulans.
Riker becomes suspicious when he learns that the U.S.S. Enterprise is escorting Romulan Ambassador Tomalak, whom Riker remembers as a Romulan captain and Federation enemy, to Outpost 23, the heart of Federation Defenses in the Neutral Zone. His suspicions are compounded when the ship's computer experiences an unusual time lag in responding to his questions about his missing years. While perusing his family records in search of clues to his past, he realizes the entire story about the virus is a charade when he discovers that the image of his late wife is actually a woman he once created using the equipment in the Holodeck.
Riker finds Tomalak on the Bridge and reveals his discovery of the charade, and at that moment the image of the bridge disappears, revealing a Romulan Holodeck. Tomalak explains that Riker was captured during the Away Team mission and that they created the images of the ship and crew by perusing his mind with neural scanners. Riker is then placed in a cell with a boy who appeared as his son in the charade. The boy, Ethan, explains that he was captured with his parents, who have been taken away.
When Tomalak returns to the cell and demands to be told the location of Outpost 23, Riker escapes with the help of Ethan. While they are in hiding, Ethan accidentally refers to Tomalak as an ambassador, when in reality he is a commander and was only an ambassador in the aborted Romulan charade. Riker catches the boy and calls his bluff, realizing that the boy is not an innocent hostage. At that moment, the scene around him fades to reveal the cavern on Alpha Onias III where the original Away Team mission was aborted.
Ethan discloses that when his people were invaded, his mother brought him to the planet for safety, leaving him with a scanner to protect him and give him everything he wanted. He lured the U.S.S. Enterprise to Alpha Onias III and kept Riker to have a companion. Riker then invites the boy to return with him to the U.S.S. Enterprise. The boy reveals his true form, as an alien named Barash, and the two transport hand-in-hand back to the starship.