John and his sister Page are living with their great aunt Beauregarde after the death of their parents in the grimy and depressing town of Pludgett. John works for the family business, building coffins, but he has managed to keep Page in school. When Beauregarde tells the two that Page will start working for Coggin Family Coffins, the two decide to run away. Luckily, they have just met Boz, and odd man who is associated with the Wandering Wayfarers circus, and he arrives just in time to drive them away from their aunt in a horse drawn fire engine. The two find the circus amusing, and John works hard to earn acceptance by the group by working on a steam driven vehicle called the Autopsy, but he is never able to make it work, and soon he and Page are on their own again. Luckily, they manage to find Maria, who runs a bakery and takes a liking to both of them. She puts John to work, but her nephew soon arrives and realizes that money is very tight. In order to help, John tries to create a new oven, but his efforts wind up blowing up the bakery! On the run again, they join up with an archaeologist, Miss Doyle, but are soon located by their great aunt and kidnapped. With the help of Boz, as well as others he has met on his journeys, John tries to create a vehicle that will steal the show at the Pludgett Day celebration and win his freedom and that of his sister.