The Christmas saboteur is fixed, but when the whole Järnkroken is to be redecorated, Maja and Leo make new discoveries that change everything. Especially for some of Järnkroken's residents.
Time to decorate the Christmas tree and Lugna gården tries to agree on what it should look like. At the same time, Trond has decided that the children will be homeschooled, which does not fit the children's plans for the day at all.
Eskil comes with evidence that gives the children new clues. In search of the saboteur, an elf leads them all the way to a treasure hideout. The masked villain must finally get caught.
Eskil becomes increasingly suspicious in the children's eyes and they decide to embark on a reconnaissance mission that must take place during the Lucia train.