An Away Team led by Worf, investigates a barren planet once inhabited by the Koinonians, a race which destroyed themselves in a lengthy war. While exploring an underground tunnel, archaeologist Marla Aster is killed by a bomb buried years earlier beneath the surface. Worf, though injured in the blast himself, feels he is to blame for the tragedy, despite Picard's assurances that it was an accident.
Lt. Aster is survived by a son, 12-year-old Jeremy. Together with Troi, Picard informs the child of his mother's tragic death. Knowing that Jeremy's father is also deceased, Troi is concerned by the child's stoic reaction to the news. Worf, himself an orphan, feels a special kinship with Jeremy and tells Troi of his wish to perform a Klingon ceremony, the R'uustai (or Bonding), with the boy.
A short time later, Troi detects an alien presence on board the U.S.S. Enterprise. In his quarters, Jeremy senses a movement and turns to see what appears to be his late mother, telling him that they are both going to leave the starship and live on the planet. When Worf discovers Lt. Aster's impostor, she vanishes. She later reappears and transforms Jeremy's room into the Aster home on Earth, as the confused boy rushes to the warmth of his "mother's" arms.
Determining that an energy beam from the planet is powering the image of Aster, Picard orders the crew to sever it. Undaunted, the energy field then gathers into a glowing mass, enters the ship and tries to gain control of the transporter room, while Jeremy and his mother hurry toward it to make their escape.
When the alien Aster is trapped in the Enterprise's forcefield, she confesses that she is part of a lifeform that survived the Koinonian Wars. In an effort to prevent further suffering from that conflict, the being recreated Jeremy's mother and home to comfort him.
Wesley Crusher, who suffered the loss of his own father, joins Picard in explaining to Jeremy that it is part of being human to mourn and feel pain, as well as joy. At first torn between his "mother" and reality, Jeremy soon decides to stay on board the U.S.S. Enterprise. After the lifeform leaves the ship, Worf performs the R'uustai with Jeremy, making them brothers forever.