The episode begins with Sandra checking in on Mark, who, in the aftermath of Naia's death, refuses to process the tragedy and instead focuses intently on the case at hand. Thoger Staal, a bird-watcher and the perpetrator of heinous crimes, has confessed to his atrocities and taken his own life. The duo attempts to question Aksel as Le makes her presence known. She tries to connect with Mark, bringing up the funeral, but he tries to act normal for her sake.
Alone, Le listens to all of Naia's voicemails, which are mundane but elicit an emotional response from her. Sandra reminisces about Naia, revealing that she was a skilled hacker who got busted. It was Naia who gave Sandra a second chance and got her into the force. Marie hopes to finally move on and decides to paint Emma's now-empty room. She feels lonely as Thor constantly spends time with Michael's wife, Louise, while Molly is out with her friends.
Sandra and Mark uncover that the dead children were found in large nests like Zara's. The nest's secrecy suggests that the stalker either knew Staal or had access to the case files. Lars Thulin, Naia's father, was working on the 1992 case and had a list of possible accomplices. One is Bjarke, the teacher who taught the kids about the cuckoo. Another is Winnie Madsen, a neighbor and bird-watcher who initially defended Staal.
In 1992, Aksel had collected 5-6 blood samples, and Mark asks forensics to compare them without Esra's permission. Esra finds out and scolds Mark. In an attempt to convince her, Mark becomes aggressive again. Esra is worried about him and can't trust him when he's emotional. She takes him off the case.
Regardless, Mark goes to talk to Bjarke and learns much. Staal's daughter, Thea, was in Bjarke's class. Everyone in school knew the counting rhyme. And Winnie knew Staal best. When questioned, Winnie feels guilty for defending Staal. She insists he was a loner and had no accomplices. She has some theories but she's a conspiracist, and Mark realizes he has hit a dead-end for the day.
It's time for the funeral, and Le eagerly waits for Mark to show up. He finally arrives in the middle of the service but is overwhelmed and leaves when he sees Le looking at him expectantly. Signe checks on Marie and is bitter about how close Louise and the kids have become and how Michael has moved on. Marie is still struggling, and Signe distracts her with small talk.
Alone, Marie sets up Emma's room to rent it out. She finds a note that says, "Stay gold girl, Your Roy." Emma's calendar shows that in August 2023, she had babysat for Roy. No one is at Roy's home, and Marie tries to snoop around when someone watches her. Signe calls and convinces Marie to go home.
Still on the case, Sandra discovers that Staal's DNA matches the one found under Emma's nails. It's a woman, and Mark realizes that the stalker-killer is Thea Staal. Marie goes home and looks into Roy when Signe shows up. Signe says "cuckoo" as a playful way to introduce herself. Marie reads more and is shocked to learn that Roy was married to Signe. Signe wishes Marie had left the case alone and then tases her.
