Now a young boy, Stephen, regularly bullied at school and bored with his home life, is informed by his best friend Keith Hayward, a snobbish and domineering neighbour, that Keith's mother is an undercover operative working for the Germans.
When snooping in Keith's mother's room, they find her diary which contains a small 'x' marked on a day of every month (however this is in reference to her menstrual cycle).