I am reading AVI - Afraid of the Dark? (AVI-E4)

Marte and Hidde are on vacation. But then something happens to Dad, and Marte is the only one who can get help. But then she has to go through the woods in the dark… alone! Will she dare?

Marte is afraid of the dark.

Her twin brother, Hidde, teases her about it.
So they go to a cottage in the woods for a week.
Something happens, and the lights in the park go out.
There's only one solution.
Marte has to go through the dark alone…