Clock watching

Dr Popovik turned a little dial on the lectern, and slowly the clock wound back. It was a cruel trick, she knew, and self-defeating. She had her bit of fun, and the students got grumpier and harder to teach, and she reached for the dial again to keep herself going. She couldn't give it up. The looks on their faces, baffled, aghast, were just too much. And on the second row there was this girl, who saw ten more minutes left than she expected, and smiled.