Carl who lives a pretty isolated life - his main contacts are his naive little sister Sofia, and his stressed out dad Jesper.
But then his class gets a new substitute teacher, and she turns out to be both mean and merciless. She wants to train the class for an international competition, and on top of that, she can read the children's minds!
The kids try to tell their parents that the substitute is not just another substitute but a creature from another world. Unfortunately, she has the parents convinced that she is nice and charming.
Of course the parents don't believe them and think the children are imagining things because they have seen too many crazy movies and played too many weird computer games.