An away team performing a scientific investigation of a deserted planet once inhabited by a race called the Koinonians accidentally triggers an ancient mine, and ship's archaeologist Lt. Marla Aster is killed. In Sick bay, Lt. Worf, the leader of the away team, reports to Captain Jean-Luc Picard that Aster was only 3 meters away from him when the explosive went off, adding that nothing showed on their tricorders and that there was no warning.
Sadly, Aster has a 12 year old son, Jeremy Aster. Jeremy's father is also deceased, making an aunt and uncle on Earth his only surviving relatives. Picard goes to see him, on the way telling his ship's Counsellor Deanna Troi that he has always felt that the Starfleet policy of having families aboard starships was a questionable one. He knows Marla Aster understood the risks as well as her own duty and Picard's, but he wonders if Jeremy will understand as well. Troi assuages his concerns, observing that Jeremy will understand these things, given time. Saying that he wants to find out what happened, Picard calls the bridge and assigns Enterprise Chief Engineer Lt. Commander Geordi La Forge to lead another away team to the dig site.
At his post as Helmsman, acting Ensign Wesley Crusher overhears Picard's order and reminds the ship's First Officer Commander William Riker that Picard also once had to give Wes similar news. He asks Will how a Starfleet officer ever gets used to telling family members that they have lost a loved one, and Riker replies that you hope you never do.
Jeremy seems to take the horrific news well, only commenting that he is all alone now, but Picard hastens to reassure him that on the Enterprise no one is ever alone.
In 10-Forward, Enterprise Operations Officer Lt. Commander Data asks Riker why familiarity with a person should have some bearing on death. He admits that he doesn't have the same sense of missing someone's presence with Aster's death as he did with Tasha Yar, and says that he can't explain it. Riker replies that it's human nature to feel a loss more intently when its a friend. Data questions this, asking Riker why the feelings shouldn't run equally deep for all losses regardless of who has died. Riker wryly observes that maybe they should, if we all felt any loss as keenly as we feel the death of someone close to us, perhaps human history would have been a lot less bloody.
Geordi returns to the ship with a "souvenirâ, one of the six explosive devices his team found. They are puzzled however, by the fact that all the devices seem to have been disarmed and pulled from the ground since Astor's accident, as if they were intended to be found, a seeming impossibility on a planet which registers as having no life forms.
Troi visits Worf, who is having difficulty reconciling the death of someone on a team he commanded. He tells her that he is angry over Astor's pointless and senseless death and can't take revenge against an enemy who became dust long ago. He adds that he wishes to make R'uustai on Jeremy, a Klingon bonding ritual where the orphan would be adopted as a part of Worf's family. Deanna suggests the two talk, but warns Worf that the boy might not be emotionally ready. Worf replies that both he and the boy are orphans and that he believes Jeremy will understand.
Worf goes to the Aster quarters and speaks with Jeremy, telling him that both of them must bring some meaning to his mother's death, suggesting that perhaps they can do it together.
Troi consults with Picard in his ready room, telling him that she is worried about Jeremy, feeling that the boy is holding on to his emotion of anger, which he must release to begin the healing process and move on. She suggests that Jeremy speak with Wesley Crusher who went through the same grief process when his father Jack was killed several years earlier. In the midst of their conversation, Riker calls Picard to inform him that an energy field has been detected on the planet. Picard steps from his Ready Room out onto the Bridge, where Data informs him that a beam of highly charged particles is emanating from the field. Troi adds that she suddenly senses a presence on the planet, and Geordi calls on the intercom to add that he's getting an unusual magnetic flux reading on the antimatter containment pods.
In Sick bay, Chief Medical Officer Dr. Beverly Crusher asks Wesley if he would talk to Jeremy, Wes says he will think about it, but the similarity of the whole situation to what they both went through years earlier dredges up painful feelings for both of them.
In the Aster quarters, Jeremy is watching some old visual records of his mother and himself in better times. Suddenly, Marla Aster reappears and says that she is back to take care of him. Jeremy is confused, telling his 'mother' that he was told she was dead. She says that this was a mistake and they are going to go live on the planet now. They start for the door, but Worf comes in and after getting over the shock of seeing a 'dead' woman suddenly alive again, reports what is happening to the Bridge. Picard tells Worf not to interfere, and Marla and Jeremy head for the Transporter room. Once there, Picard arrives, and faces off with the duplicate Aster, telling her that he does not know who or what she is. Worf lunges and grabs Jeremy away from her, and she disappears.
Troi takes Jeremy back to the Aster quarters, but when they arrive, the room has taken on the exact appearance of the Aster's home back on Earth. Marla has returned once again! Troi, knowing that this is some kind of construct, calls Picard to let him know what's going on, and asks the boy not to stay there. On the Bridge, Riker ironically observes that they are at a great disadvantage, while the manifestation of Aster can offer her son pretty much anything, they can only offer him the cold reality of his mother's death. Geordi realizes that the odd readings he noted earlier were indications that the ship's own energy is being tapped to create and sustain the manifestations 'Marla Aster' is creating. He tunes the harmonics of the ship's protective deflector shields to be the same as the anti-matter containment pods, which blocks the particle stream and ends the simulation.
All at once, a filament of plasma comes up from the planet, striking the ship and penetrating it. Again the Aster quarters reverts to the simulation of the Aster household on Earth. Troi reports to Picard that the apparition of Marla Aster is once again aboard the ship. As the Asters again start for the Transporter room, Picard orders containment force fields raised in the corridors and goes to confront Aster. When he arrives, Marla tells him that at one time two races existed on the planet below, one of physical beings, and one of energy. After watching as the physical beings destroyed themselves with unending wars, the energy beings wished to prevent any more suffering due to that dishonorable past, and so they decided to aid Jeremy Aster with the horrible tragedy of his mother's death. Picard says that he appreciates their motives, but he and Troi point out that these aliens can't possibly realize the enormity of the undertaking which they are proposing. Deanna asks the duplicate if she and her people are ready to foster Jeremy for the rest of his life, providing friends, a career, even a wife. Picard adds that dealing with death and suffering are a part of the human condition, and says that Marla is offering Jeremy a memory, something humans cherish but cannot live in. He then calls Worf on the intercom and asks him to bring Wes to the Aster quarters. When they arrive, Wes describes his experiences when he lost his own father, admitting that he was angry at Picard since Jean-Luc had led the mission where his father was lost, he was mad that Picard came home and his father didn't. Hearing this, Jeremy admits that he's angry in the same way at Worf. Troi points out to Jeremy that Worf lost his parents too. Worf adds that he was only six, and that humans helped him when he was alone. He tells the boy that the real Marla Aster now only lives in their hearts and asks Jeremy to join his family for all time through the R'uustai in her honor. He also tells Jeremy that the ceremony will make the two of them brothers.
The manifestation of Marla Aster realizes that it has made a mistake, and after one more loving touch of the boy disappears, along with the rest of the reality it created.
Later, Worf and Jeremy perform the R'uustai ceremony, lighting candles together. Worf places a Klingon sash bearing the crest of the House of Mogh on the boy and in the Klingon language says âSoS jlT batlh SoHâ. Jeremy asks him what he said, and he replies that he was honoring the memory of their mothers, indicating that the two of them have now bonded, making their families stronger. Jeremy then respectfully repeats the Klingon words which Worf spoke.