Story number thirteen sees Anne and George staying at a
riding school whilst the boys are away at camp.
Of course, George is not at all happy about this and even more annoying for her is another girl at the riding school called Henrietta. Henrietta is a lot like George in many ways - she, too, likes to strut around like a boy - and, like George,
insists on being called "Henry!"
George cheers up when they receive news that the boys are going to join them to finish their holiday together. When the boys arrive, Henry meets them in the town and they assume she is a boy - MUCH to George's annoyance!
They all take a horse ride onto the nearby Mystery Moor where they come across a group of travellers. They learn that this particular group regularly turn up on the moor but nobody can understand why! There is absolutely nothing there!
Whilst camping out on the moor, and watching an aeroplane dropping mysterious parcels, the Five discover the reason
behind the travellers' regular visits to the moor.
One of the travellers' children - a boy known as "Sniffer who takes a liking to George - helps the Five to solve the mystery.