In the year 1400, a young man came to the door of the largest hospital in Siena. A plague was raging through the city so horrible that as many as twenty people died each day just in the hospital alone. And many of the people who died were those who were needed to tend the ill. It was a desperate situation — more and more people were falling ill and fewer and fewer people were there to help them. The twenty-year-old man who stood there had not come because he was ill but because he wanted …