Kat is attending a sleep-over with three of her friends from school, at Jenny Woods' house. The girls are in Jenny's bedroom in their pajamas, and are playing with an Isis Board (similar to a Ouija board). When Alana says it's now Amber and Kat's turns, Kat doesn't want to do it, not because she's afraid (as her friends accuse her of), but because she's not supposed to. But pressured by the others, she tries it. As Amber calls out for any spirits present to speak to them, Kat seems to fall into a trance and begins humming a lullaby, "go to sleep, my Celinda..." A wind blows out the candles, and the other three girls scream as a figure materializes over by the window, a figure of a woman that suddenly disappears as Jenny's mother comes in. Kat falls to the floor in a faint.
Back in her own bed, Rachel is trying to figure out why Kat fainted. She tells Kat that her friends figure it was because she was scared, but Kat (who is oddly uncommunicative) says that they were the ones who were scared. When her mother quizzes her further, she claims that nothing really happened. They were playing with Jenny's Isis board and they got scared. As soon as Rachel leaves the room and turns off the light, Kat jumps up and rushes over to open her window, gazing out as if looking for something--or someone.
At the Legacy house the next morning, Nick, Alex and Derek are discussing investigating a charlatan. Rachel rushes in, apologizing for being late and tells them about Kat's difficult night. When she mentions the Isis board, Derek becomes concerned and asks if Kat used the board. Rachel tells him that Kat really didn't say, which strikes her as being unusual for Kat since they talk about everything. Derek points out that for Kat, this kind of thing can be extremely dangerous. "She may have experienced something she's afraid to put into words." He tells her it happened to him, when he was a boy. Alex reveals that at Kat's age she started feeling responsible for the things she saw, and didn't feel that she could talk about it with anyone. When Derek suggests that Alex talk with her and maybe bridge the gap, Rachel agrees.
Alex finds Kat downstairs making a "monster sandwich." When Alex asks her about the Isis board, Kat gets defensive. "It was only a game. Why is everyone making such a big deal out of it?" Alex tries telling her that, when she was her age, she used to think things were her fault and she just wants to reassure Kat that that isn't the case. But Kat doesn't want to talk about it. When Alex attempts to let her know that these things can be dangerous for her and they need to know about them for her own safety, Kat gets upset. "They're my friends! You don't understand, you're gonna get them into trouble. Just leave me alone!" she cries, and runs out.
Rachel believes that since Kat doesn't have many friends she feels she needs to protect the ones she has. Derek insists that she needs to understand that the only way she can protect her friends is to tell them exactly what happened. Alex feels that something did indeed happened, so Rachel thinks she may not be being over-protective after all. Derek observes that the girls seem more concerned with what their parents are going to think that with what went on. If something did happen that night, there is the possibility that Kat won't be able to protect her friends--or herself. Rachel agrees to keep an eye on her. She gazes with worry and fondness on Kat, as she and Nick come into the room playing airplane.
At home that night the ghost appears in Kat's room while she's asleep, waking her singing the lullaby. Kat goes up to her, asking her who she is and what she wants, but the ghost only strokes her face and continues to sing the lullaby, then disappears. Kat looks out her window but sees nothing.
In the library at school the next day, the girls say they all saw the ghost the night before and are wondering who she is. When Jenny says she thinks they ought to tell their parents, Amber says they'll only get in trouble if they do and Alana agrees. Kat points out that the ghost is not really scary and she thinks they should wait and find out what she wants. "Then we'll know what to do." They make a "pinky promise" not to tell, but Jenny still looks very scared. Kat hugs her and tells her not to worry. "Nothing bad will happen."
As Jenny's mom is getting her ready for bed (in her room with the Isis board), Jenny asks her if she can sleep with her and her dad that night, saying she doesn't like sleeping by herself. When her mother asks if anything is wrong, she says she just doesn't want her to go is all. But her mother holds firm, kisses her goodnight and leaves. The ghost immediately appears at the window, singing "Come to me, my Celinda..." and holds out her arms to Jenny who, in a trance, goes to her. The ghost picks her up. Jenny's mom comes back to say if she's really afraid it's all right with her dad if she sleeps with them--but Jenny is gone.
Rachel, in response to the message on her machine, comes over the next day to learn from a tearful Mrs. Wood that the police have found nothing. She says Jenny was frightened, and blames herself for not listening, for not letting Jenny sleep with her.
Derek and Rachel go to the school to talk to the remaining three girls to ask if something unusual happened at the party that night, and get them to admit to using the board and bringing the ghost. Kat blames herself, thinking she's responsible for bringing her. The ghost is very angry, and very sad, she says. When the bell rings, the girls rush off in relief. Derek thinks that under the circumstances, Kat and Rachel should stay at the house, and they should call Jenny's mother and ask to see the Isis board.
Alex has discovered that the Woods' house was used as a brothel in the 20s. And while the Isis board turns out to be just a simple game board, Derek receives visions from the planchette, of a little girl being abducted. He thinks it possible the other girls are in danger, and wants to have them stay at the Legacy where they can be protected. Nick goes to pick them up.
Mr. Gannon, Alana's father, is openly scornful and, with a sick baby and a stressed-out wife, refuses to allow Nick to take his daughter anywhere. Suddenly on the baby monitor they hear a lullaby being sung, and as the parents rush upstairs Nick runs outside to see the ghost carrying Alana out of the house. The ghost becomes angry and tosses Nick across the yard when he comes too close, and the parents get there just in time to witness the ghost and their daughter disappear.
At the Legacy the next morning Nick reports to Derek and Rachel what happened at the Gannons', and Rachel agrees to try again to get Amber's mother to allow her to bring Amber to the island. Derek hopes, since the abductions took place when nobody else was in the room, that perhaps the presence of others will deter the spirit. Rachel is skeptical, after what happened to Nick. Derek insists they have to be ready to confront it, communicate with it, and figure out what keeps it in a state of unrest. Rachel is horrified to realize Derek wants to use Kat as "bait" to lure it out. He points out that until the ghost is put to rest, there is nowhere she can take Kat that the ghost won't follow. They can't run; their only chance is to stay and fight.
Alex's research uncovers the story of a prostitute named Alice Burke who worked at the Wood house when it was a brothel in the 20s, and who refused to give up her child for adoption. She threatened to name the prominent father, who denied paternity. Alice was tried and imprisoned for prostitution. Her child, who would have been nine years old, was taken from her and probably sent to an orphanage. Derek believes their only chance is to reunite Alice with her lost daughter, who Nick points out would be about 80 years old if still alive.
Amber has been brought to the house, and while disappointed that Rachel won't let them explore the place seems to be settling in. The adults arrange protection outside the door in shifts, with Rachel in the room with the girls at all times. Nick wonders at the wisdom of keeping both girls together, but Derek points out that splitting them up would spread them too thin, despite the danger that they could lose both girls. There is no choice: they have to stop it.
The girls are awakened by humming, and the ghost appears. Rachel awakens in time to pull Kat back from her. Derek and Nick burst into the room, Derek crying out to the ghost that they know who she is and want to help her. But she doesn't listen; she throws the men back, and picking up Amber cries out "You can't have her!" Derek tries to get her to see that it isn't her daughter, but the ghost disappears--taking Amber with her.
In the library the following morning, Derek says it appears the ghost of this woman is reenacting the horrific abduction of her own daughter. "By abducting someone else's child?" Nick asks. "It doesn't make sense." They realize that it isn't really an abduction, but Alice Burke reliving her own experience. "Taking the child back for her is an act of protection." Rachel points out that she repeats it now in the vain hope of recapturing the child she had lost. She won't stop until she has Kat, and if she succeeds, Derek says, they're gone forever. Their one hope is to find the nameless daughter taken from her so long ago. Kat tells them she's not nameless; her daughter's name is Celinda, she sings her name in the lullaby.
Alex finds at the orphanage that Celinda Burke wasn't adopted so still has her original name, and that her Social Security number is listed. With that in hand she returns to the Legacy where she, Nick and Derek discover a current address through tax records. He sends Alex and Nick to bring her back to the Legacy, while he stays to try to protect Kat and Rachel if Alice Burke's ghost reappears.
Alex and Nick find that Celinda Burke is very bitter about being abandoned by her mother and at first doesn't want to talk to them. Her mother lied, she says; she promised to come back for her and never did. Nick tells her that's not true, and they convince her to listen to them.
At the Legacy, Kat is blaming herself for bringing the ghost, and feels that she's the one who has to bring her friends back, that she has to fix it. Rachel explains to her that Alice Burke is a powerful force doing terrible things, but that is because terrible things had been done to her like her daughter being taken away. She promises Kat that she will never let that happen to her. When Kat wonders why her mom can't help the ghost, because isn't that what she does? Rachel explains that how she helps is to get people to talk about their troubles so they can help themselves, and that she is afraid Alice Burke is beyond that. It's so unfair, Kat says; the ghost is so sad, and now she's making everyone else sad. Suddenly lighting flashes and thunder crashes, frightening Kat. The front door bursts open, and Kat feels the presence of the ghost. "You've gotta help her!"
Alice Burke appears and beckons to Kat, singing. Kat, in a trance, begins to go to her but Rachel holds her back, trying desperately to get Alice to listen to her and realize Kat isn't her daughter. Derek comes downstairs and calls the ghost by name and tries to convince her they can help her, that this is not her child and they can help her find her real daughter, but she throws him violently back against the wall where he lies unconscious. Turning again toward Kat she causes all the doors to slam shut and approaches, singing the lullaby. Kat, entranced, breaks away from Rachel and goes to her. Rachel cries desperately to get her to stop, to listen; appeals to her as a mother, and she seems to be getting through for a moment. Then Alice cries out, "I won't let you take my baby!" Kat comes out of the trance and tries to reach out for Rachel, and when it appears Alice might win and take Kat away a voice calls out timidly, "Mother?"
Nick and Alex have returned with the 80-year-old Celinda Burke, who comes forward in wonder. "Mother? Is that you?" The ghost turns to her, and recognizes her child. Derek comes to in time to witness mother and daughter approaching each other. "I missed you so much," Alice whispers yearningly. "I waited, every night, but you never came back," Celinda tells her. "Come to me," Alice says, holding out her arms, and Celinda becomes again her nine-year-old daughter as mother and child are finally reunited. They disappear, embracing, and the three missing children reappear. There is a happy reunion between Kat and the girls, who feel they've been having a strange dream about a ghost.
Rachel's journal entry is heard over this reunion, with Rachel and Derek looking on.