Absalons secret

This year's Christmas exhibition in the department store is to be opened and Cecilie has been given the task. During the opening, Petra is asked about Absalon's secret, but she dismisses the questioner, but Cecilie thinks Absalon's secret sounds exciting. During the opening, a mysterious boy also appears, but quickly disappears again. Amir is worried because things are disappearing from the department store, but dad doesn't think it's a problem.

Cecilie sees the boy again and he runs away but knocks over a stack of cans on the road. Petra talks about Absalon and his time while Cecilie has a flashback to the same time period. Both Niels and Benedikte are stressed about buying gifts and Benedikte thinks the parents should stop giving each other gifts. Cecilie wants to go to the ruin but Amir stops her and when she meets the boy again she promises not to reveal him.

Cecilie has heard a secret about the dungeon and gets help from Hubert to get into the basement. When they are standing at the entrance to the ruin, they still don't dare go in. Hubert also soon gets scolded by Frode because Cecilie is in the basement. Up in her room, Cecilie makes a map of the basement and talks to Ida about the project.

Mother talks seriously with Cecilie and Ida about the ruin and when mother has to go to a meeting she asks Cecilie to look after Ida. Ida goes into the basement and down into the ruin so when Cecilie discovers it, she sets out after Ida with help from Hubert. At the last moment they find Ida who is very ill again. This makes Cecilie pack up all her archaeological things and declare that she does not want to be an archaeologist anymore.

Hubert believes the secret can make Ida well because she is an angel. He knows this from a letter Frode has and Cecilie seeks out the three in the basement for help. But Frode only has part of the old letter from Margrete the first. Meanwhile, Amir gets more people to help solve the many thefts from the department store.

Cecilie 'borrows' her father's key to the exhibition so that she and Hubert can get to Absalon's stav. Here they find the second part of Margrete's letter. Down at Frode and Ib's, the four of them read the letter and discover that the children are going to Roskilde Cathedral the next day. Meanwhile, Amir believes that the thefts are being committed by the store's own employees, but this is denied by Niels.