The Olsson family is tired of sitting in the apartment in town and decides on a white Christmas in the country. In the newspaper they find an advertisement
Lillan gets a voltmeter from a classmate and discovers that it's haunting. After an unsuccessful attempt to be intimidated, the ghosts Jean and Staffan decide to take on the hard gloves.
Ivar and Lillan go ghost hunting. Melitta, who is afraid of the ghosts and wants to go home, enlists the help of the newspaper courier Måns to prove to her parents that the ghosts are real.
The ghosts are stuck in the family's computer, but Lillan decides to let them out after a classmate says it's animal cruelty. Leif has put the thing together Lillan and Ivar found it in a coffin.
The children try to figure out how to get the key and free Dioda. Astrid thinks that the children drink too much Christmas must and intends to show that it is bad for the teeth.
Leif and Astrid have realized that it's haunting Greveholm and are terrified. They want to go home but the children refuse. Can Melitta, Ivar and Lillan convince the parents that the ghosts are not dangerous before Christmas Eve?