This book is about the vicissitudes of a family that moves to "Tre camini", a house near the railway. The father, who works at the Foreign Ministry, is imprisoned after being falsely accused of espionage. Children make friends with an older gentleman who takes regular train of 9.15, near their home. He helps the kids to prove the innocence of their father, and the family is so convened. The family has a Russian exile, Mr Szczepansky, who came to England looking for his family and Jim, the nephew of the old gentleman, who is suffering from a broken leg. The book is about two subjects: the innocence of a man unjustly imprisoned and the prosecution of a Russian exile, persecuted by the Tsar.