On many a dark night people would see her walking along the riverbank and crying for her children.
A father and son go fishing at the river and see a woman in white walking along the riverbank and crying. She walks into the water and the father, Luis Alvarez, goes to rescue her. She sinks beneath the waters before he can get there and Luis dives under and tries to find her. As his son Rafael calls to him, Luis dives under repeatedly. When he comes up, Luis sees the woman in white on the shore, leading Rafael away. Luis runs after them but by the time he catches up, they have both disappeared.
At the trailer, Nick takes out a flail and drives to Eddie's house. The Blutbad has decorated his house to extremes for Halloween and talks about the Wesen tradition of chasing villagers through the woods. Eddie admits that he doesn't do it in Portland these days and then gets the flail from Nick as a decoration. He puts it on an automaton and takes Nick inside, and demonstrates how he's rigged it to swing at a nearby pumpkin. The station calls to tell Nick that he has a case and he leaves after making Eddie promise that no one will get hurt.
The Woman in White lies beneath the water. She transforms into a ghost, shrieking...
... and detective Valentina Espinosa wakes up from her nightmare. She looks at her board, which has reports of missing children across the northeastern U.S.
Nick and Hank arrive at the river and meet Wu as he questions Luis without success since the man doesn't speak English and Wu doesn't speak Spanish. Wu informs the detectives that Luis disappeared and they've called in search-and-rescue. However, kayakers saw Rafael come up from the river and took some video. On the video, they see the Woman in White leading Rafael away. Nick tells Wu to bring in their translator but he's away on vacation so Nick calls Juliette and asks her to work as a translator.
Back at the station, Hank and Nick tell Renard what they've found out so far. The intern, Ryan, comes in to tell them that Juliette is there. He hesitates and Renard tells him to usher her in. She stares at Renard intently for a moment and he stares back, and then they take her to Luis. Translating, she explains that Luis went to help a woman who then walked off with his son. Luis doesn't know the woman and his wife is dead. They have Luis take them to his home so they can try to find a lead.
Valentina gets an alert about a new missing child on her computer. As she looks at it, she transforms briefly a jaguar-like Balam and then books a flight to Portland.
Luis takes Juliette and the detectives to his home and discover that the neighborhood is celebrating the Day of the Death. Rafael isn't there and they check the boy's room. They get a photo of Rafael from a family photo. Meanwhile a woman, Pilar, approaches Juliette and expresses her condolences about Rafael's disappearance. She says that she knows who took Rafael but Rafael insists that she doesn't know and isn't helping. The detectives tell her to talk and Pilar describes the legend of La Llorona, a dead woman who steals children and cries. Pilar insists that La Llorona took Rafael and she confirms that the woman in the video is La Llorona. Wu starts canvassing the neighborhood and Hank assigns a detective to stay with Luis in case anyone contacts him.
As they leave, Pilar sees the cat scratches on Juliette's hand and says that she was very sick and has lost her memories. Juliette doesn't want to talk about it but Pilar says that she must believe that someone did it to her. Nick asks if Juliette can stay until she finds another translator and Juliette agrees, but refuses to discuss the rest of what Pilar told her.
Renard is in his office on the phone, talking to one of his people who says that they have to make sure that Duvall didn't give up any of their names. Ryan interrupts to tell Renard that Valentina is a police detective from New Mexico with information about the abduction. Renard meets with her and Valentina says that she can help them with Rafael's abduction.
Nick and Hank are working the phones when Renard brings Valentina over. She explains that they can expect two more abductions before the day is over, and that the Woman in White has struck in other cities. Valentine warns that Rafael and the other two victims will be dead by the next morning if they don't act fast.
In a boathouse by the river, the Woman in White kneels over Rafael and strokes him gently. As he looks up at her, she transforms into a hideous creature.
Trick or treaters show up at Eddie's house and he activates his pumpkin mashing dummy. He dresses as a skeleton and serves them candy. As they go, three bullies pick on one of the girls, stealing her candy. When Eddie tells them to give it back and they refuse, Eddie grabs one of them and forces him to give the candy back. The kid promises that Eddie will be sorry and walks off with his friends.
Valentina explains that her unsub always abducts two boys and a girl, and they all turn up drowned. They're always abducted before midnight on Halloween, and she shows them the only image that she's compiled from eyewitness reports. Nick shows her the video and as Valentina watches it, Nick sees her briefly reveal her true face. They figure that Rafael was the first one taken and Valentina says that the children are always taken near where two rivers meet, in the same triangular pattern. In each case, the witnesses heard the woman crying and thought she was trying to kill herself, and she always kills her victims at the same time. Franco calls Renard away and Nick asks Valentina about La Llorona. In the stories, a mother kills her children when her husband leaves her for another woman. However, Valentina insists that it's just a legend and the killer they're dealing with is real.
In his office, Renard tells Franco to get everything they can on Valentina. Once Franco leaves, Renard goes over a report on Adalind saying that she's been in Vienna recently.
The children continue trick-or-treating in the woods. One girl, Kalli, goes off on her own and hears the Woman in White crying as she stands at the shore. The Woman offers Kalli her hand, smiling.
Valentina works with Nick and Hank to pinpoint the approximate area that the Woman will strike within. According to all of the reports, the Woman simply appears and then disappears with her victims. Renard tells them that they've gotten a report on another abduction and it fits the pattern that Valentina has described.
The detectives call Wu and tell him about the new abduction. He tells Juliette and has her translate for Luis. Pilar comes in with a gift of food and Luis angrily tells her that he doesn't believe in her ghosts. He storms out of the room, crying. Meanwhile, Pilar tells Juliette that she is trying to work out what she understands and what she doesn't. Pilar warns her that her world is coming apart and that she will have to choose between two that she feels for. Juliette insists that she isn't choosing between anybody and Pilar leaves.
An officer takes Nick, Hank, and Valentina to the abduction site. A guy fishing down the river saw the Woman and they go to talk to her. Renard arrives and tells Valentina that he's checked and that the only Valentina they have left the force three years ago. The FBI want her held on the grounds of impersonating an officer while they take over the case. Renard orders Hank and Nick to hold her, but Valentina insists that they have to stop the Woman. She starts to transform and Nick warns her not to do something she'll regret. Valentina thinks that Nick plans to kill her, but Nick says that he just wants to get the kids off and they'll shoot her if she puts up a fight.
The woman takes Kalli to the boathouse and lies her down next to Rafael.
Renard interrogates Valentina and wonders how she knows so much about the Woman. He points out that she was fired because she was obsessed with the case and asks where she was when Rafael was abducted. Valentina explains that her sister's child was taken five years ago and that the boy was with her that day. She saw the Woman and lost her nephew, and warns that a third child will be taken. Renard says that it doesn't matter and that she'll be detained until the FBI are ready to speak to her.
That night, more trick-or-treaters return to Eddie's house. The three bullies from earlier lurk outside and plan their revenge.
Nick and Hank figure that Valentina is right and wonder how they will cover the waterfront. They go to the trailer and check the journals, and find an entry on a ghost called La Llorona. She takes three children on All Hallow's Eve and the journal shows a symbol similar to the meeting of two rivers that Valentina describes. According to the journals, Nick's ancestors never figured out what La Llorona is, and she dates back to 1519 when a Grimm saw her in Veracruz. The Grimm set out to kill her and never returned. They realize that they can't let the FBI run with the case and they go back to the station.
The three bullies smash Eddie's front window and he goes out on the porch as they run away.
Nick and Hank release Valentina, explaining what they've found out about legendary La Llorona. She insists that the killer is real and they take her with them, explaining that they're going to the third part of the river. As they get to the car, they get a radio report that a Tino Diez has disappeared along the river where Valentina predicted. Valentina doesn't know where the Woman will kill the children but they realize that the Woman will drown them where the rivers meet, and they only have fifteen minutes until midnight and the Woman kills them.
The Woman takes the three children to the confluence of the rivers and calls out, asking for the return of her children, Nick, Hank, and Valentina arrive as the spirits of the three children rise out of the river. The Woman offers her three entranced children to take their places. When the trio arrive, the ghosts recede and Nick tackles the woman while Hank and Valentina pull the abducted children away.
Under the water, Nick struggles with the Woman, which lunges at him, snarling. He swims to the surface but the Woman pulls him back under. He struggles with her and she reverts to her human form and then sinks into the depths, fading away. Nick gets to shore and admits that he had the Woman and then lost her, as they realize that midnight has just passed.
Back at the station, Hank and Nick reunite the children with their parents. Juliette is with Luis and smiles at Nick in satisfaction. Ryan comes out and shakes Nick's hand, while the detectives figure that they won't know if it was a ghost for another year. Renard informs them that the FBI have arrived and they're not happy. Renard figures that they can give the FI agents some credit for rescuing the children in return for them dropping the charges against Valentina. Meanwhile, Juliette looks at Nick and remembers what she told Pilar earlier about not choosing anybody.
The three bullies look at the video they took of their vandalism Eddie tracks them down, takes the camera, and says that they'll give it back when they pay for his window. When they say that they're not scared of him, Eddie transforms into his true form and they run off in terror.