The U.S.S. Enterprise is called to aid the Dorian, a Federation ship that has come under fire while transporting a Lumerian ambassador to mediate a dispute in the Rekag-Seronia system. Picard agrees to transport Ambassador Ves Alkar aboard the Enterprise to insure Alkar safe passage. Alkar transports aboard along with his aged mother, Sev Maylor, who takes an instant dislike to Troi. After Alkar asks Troi to use her empathetic powers to help him in the negotiations between the Seronians and the Rekags, Maylor insults Troi, sure that she is attracted to her son. Upset, Troi shares her negative feelings about the old woman with Riker. Both are surprised a few minutes later when they are summoned to Alkar's quarters to find that Maylor is dead. Since she is an empath, Alkar requests she perform the customary Lumerian funeral meditation with him, a process that leaves her feeling a bit strange.
The Enterprise welcomes Alkar's two delegates, Jarth and Liva, who are disturbed by the worsening fighting between the warring factions. Alkar, however, remains calm, and even insists on going to the negotiation site without the protection of an Away Team. Later Troi joins the group, Data and Riker in Ten-Forward and shocks her crew members with her appearance and behavior. She appears to be aging rapidly and dressing more provocatively. In addition, she viciously attacks both Jarth and Liva, prompting a stunned Riker to escort her to her quarters. Once there, he is even more stunned when Troi throws herself at him.
The next day, Alkar arrives at Troi's quarters and upsets her by announcing that he is transporting to the negotiation site without her. She follows him to the transporter platform, begging him to take her with him. Picard is shocked by the change in her appearance — she is now a white-haired, disheveled old woman. Unwilling to let Alkar leave, she rushes toward him with a knife, stabbing Picard in the arm when he steps in to stop her. Security rushes both Picard and Troi to Sickbay, where Nurse Ogawa notices a correlation between Troi's condition and that of Maylor right before she died. Unable to reach Alkar, Picard instructs Beverly to perform an autopsy on the dead woman without her son's approval. Beverly soon finds that Maylor was not really Alkar's mother, but an unnaturally aged 30-year-old woman. Alarmed, Picard transports to the negotiation site and confronts Alkar, who reveals that he caused both Maylor and Troi to age so rapidly. He used these women — channeling his dark thoughts into them in order to keep his own mind unhindered by unwanted emotions and remain the perfect negotiator. Picard insists that Alkar free Troi, but he refuses, and instead returns to the negotiating table.
To save Troi and outsmart Alkar, Beverly and Picard suspend Troi in a deathlike state to sever Alkar's tie with her and force him to turn to someone else. Alkar immediately beams back aboard the Enterprise with Liva. After viewing Troi's "dead" body, he prepares to perform the funeral ritual with Liva, hoping to turn her into his new psychic dumping ground. But at the minute the transformation is about to take place, Picard transports Liva, leaving Alkar alone with his terrible thoughts. The psychic burden kills him just as Beverly revives a shaken Troi.