Ruby has discovered an old pinball machine in the basement, which she uses a little magic to breathe new life into. She has also developed a keen interest in the theory of relativity, the reading of which also prevents her from taking part in the Sunday excursion of the third year. Fenella and Griselda do not take part either, because they are busy with their history project and are not getting anywhere. If only one could travel in time! Ruby can help them by turning the pinball machine into a time machine! But unfortunately this experiment is sabotaged by Esther, which has threatening consequences.