Peter receives a model engine as one of his tenth birthday gifts. It's his favorite present, but one day it suddenly explodes with a "bang." This damages the toy Noah's Ark people traveling inside it, but nobody else is hurt. Peter, however, is very upset. He pins his hopes for repair on his father, who has been away in the country for a few days, because his father is good with repairs. He can hardly wait for him to return home.

When his father does arrive and is consulted about the engine, he is optimistic that it can be fixed. He says to Peter that all it needs is

a bit of brazing say, or some solder, and a new valve.

Peter's father says that they can work on fixing it, with the girls to help, on Saturday.

Everything seems fine when a knock is heard at the door. Father is called away from the children for a long time, and then their mother is called away. The servant Ruth, "looks queer" and thinks it is bad news. All the children hear from their mother, however, is that their father has to go away for a time. Little do they know they he has been falsely arrested.

After this, the children move away with their mother to a smaller house outside of London. They have to learn to be self-reliant because they are so much poorer.