Don't tell anyone, not even your sister...'

Jackson Fortune has always followed the lead of his tough older sister, eleven-year-old Tracey. Then he receives the first of a series of secret messages and he suddenly has a mystery to solve all by himself. Without Tracey.

But the messages to Jackson are not the only mystery. Who is the stranger on a motorbike seen hanging around their cousin Tessa's house? And why does Tracey suddenly decide she wants to wear a dress? As Jackson takes his first steps away from Tracey, only to discover that he couldn't wish for a better big sister, there are more than a few surprises in store for the Fortune family!