British Museum tour guide named Agatha in each episode guides three children from one town on a quest to help them defeat the evil Dark Lord, whose servants, cowled figures called the Dark Forces, glide the darkened corridors and display rooms of the museum. The children have only one night to discover a relic in the museum itself and they have to win three challenges.
Allis and Ann are best friends. But one day, when the girls are about twelve years old, Ann is killed in a road accident, and Allis becomes very cold inside and doesn't want any new friends. Her parents start working abroad and therefore, she has to live with her grandparents (who are the landlord and landlady of a big house) and begin going to a new school, where everybody teases her, because she is so odd and doesn't want to make friends with anyone. There is also another odd person who is teased in the class, Sigge, who is a Polish immigrant. When a bird gets hurt and Sigge takes care of it, Allis wants to help him somewhat. And after she let Sigge into the big house where she lives, nothing becomes the same and things start to happen, both in the house and in Allis's heart.