The Brutes(1970)

On the edge of a big city on a go-kart track, Mike and Werner meet Alice and her friends. They like the girl. Mike manages to separate Alice from her group and get into the car with Werner. It had been decided to go to a lake with the others to take a bath at night. Too late Alice realizes that Mike and Werner did not drive to the agreed lake, but to a lonely gravel pit. The friends will not come anymore. And she realizes the intentions of her companions.