Finley and Grandad Laurence journey back around 350 years to find out what life was like for a child during the time of the Great Fire of London. Together they dress up in clothes from the time and learn about a boy called William Taswell who wrote a diary about the Great Fire. Finley and Grandad Laurence play some fun games that William might have played with his school friends, and together they discover how the Great Fire started, why it spread across London and how people warned each other about it. Finally they discover how William and his friends helped put the fire out, and why a big fire like that can never happen again.