The Fraulein and the Sandman

One fine morning, Benno finds sand in his bed. While he tries to ignore this at first, he soon must realize that he himself is loosing the sand. Day after day the sand increases and soon his time literally starts running short. Finally he is left no choice but to ask Sandra for help, who runs a small coffee shop under his apartment. Although Benno hates her with a passion, he started having dreams of her every night. What could Sandra and the dreams have to do with the sand?