Penny and Ewan Macdonald live in a pony-less household, with 'a fridge and a washing machine but no pony.' They have resigned themselves to a summer without ponies when, on the way back from the Pony Club Rally, they come across a pony where no pony should be. There, in their neighbour's field, is a Highland pony. Miss Frobisher has agreed to look after Augustus for the summer. Augustus needs someone to look after him, and here are Penny and Ewan. Their dream has come true.

Augustus has his own ideas about all that. What Augustus likes is a nice green field, and none of this gymkhana nonsense.

Can Penny and Ewan persuade Augustus to become an ornament to the show ring, and an example to the Pony Club?