Here is the fourth book of the Trubshaw saga. Our hero is at home now for the Christmas holidays. He is a precocious twelve-year-old schoolboy, and the family has a visitor staying for the holiday, the intended bridesmaid for the planned wedding of his father. But it turns out that there is another visitor during the time he is to spend at home. This visitor is part of a test that his father had planned for his son. Will Trubshaw be able to solve...