Sir William Petty is a rather famous gentleman who, being a founder member of the Royal Society, knows the king and many other famous folk (including Samuel Pepys). Recently several of his London properties were burned down during the Great Fire. Petty tells the full and exciting story of the terrible calamity during which the children join in several activities, such as working out how to form a bucket chain and becoming houses in an experiment to see how easily the fire spread. Sir William can ask the children to help him draw a map of the new London, each child having their own little parish to re-draw which then all join together to form one large map that everyone has contributed to.