Sixth grader Gwen Baker is puzzled. Why does her history teacher, Mr. Sharp, continue to arrive at school with strange bruises? Why does he seem lost in another world so often? She knows how it began - lightning hit the school one evening when Mr. Sharp was working late. He rescued a homeless man who had wandered into the teacher workroom for shelter. But why do new bruises continue to dot his arms for weeks? Classmates spread rumors about the cause. Only Gwen and her friends Nathan and Libby have the courage to pursue the true cause that lies within the mystery of the teacher workroom. Their curiosity will take them on their own rescue mission - saving Mr. Sharp. Their adventure will also save the very existence of their town, Hazel, Kansas. Through her experiences, Gwen realizes that people in her history lessons are more than simply characters in a story. People in old photographs are, in many ways, just like her.