The cup in the Forest

I read "The cup in the Forest".
One day Per and his girlfriend Nina were near a big forest
Driving around, getting out of the car  and strolling through the forest
After going through the dim forest for a while, they found a cup.
They decided to take it back to the hotel for the museum director to see. The director tells the two to immediately return the cup to the forest.
Nina could not believe the words of the director, and was thinking of selling at a high price...
Of course I was scared of the Viking ghost, but I thought Nina was even more scared.