One golden afternoon, Henrietta Ferranti, along with her family and friends, sets out for young Hugh Anthony's birthday party, and he's going to celebrate with the people he loves best, young and old alike. The day begins with a wish and ends with a revelation after a magical mystery tour. A procession of landaus and victorias, plus one motor car, are bound for the Blue Hills and Hugh's picnic. Whatever the reason, each of the horses and ponies carrying them mysteriously lost on its way to the Blue Hills.

As each of the partygoers ventures into an enchanted forest where legend becomes reality and their wildest dreams come true, and by the time the travelers meet again over tea and iced birthday cake, they have had such adventures. Adventures such that none of them is the same person. They are wiser, nicer and much happier. The innocent birthday picnic becomes the adventure of a lifetime and no one will ever be the same again.