Peter had a happy, settled life at home with his mum, and at school with his best friend, Tom. They had known each other a long time and were inseparable. This, however, was about to change when he, by accident, spotted his mum and headteacher together, holding hands! Although he wanted his mum to be happy, Peter couldn't accept this. He and Tom decided that they should do something to return life to how it was before. Nobody would want their headteacher as their new dad even if he was a good headteacher and had improved the school's exam results. But what could they do? They try various things with no luck apart from getting themselves in trouble. Then one day the boys see one of the school's supply teachers acting suspiciously. She suddenly takes an interest in them, especially Peter. What was she up to? Could she help them? Should they trust her?