[3] It is a contemporary adventure story set on a fictional island in the English Channel during World War II and eventually during a German occupation.

[1][5][6] Penguin issued a Puffin Books edition under the original title in 1964, with illustrations including colour plates by Elisabeth Grant.

The Pony Club's chairman, Peter Beaumarchais, has surprisingly opted for a fancy-dress carnival as their Anniversary Day celebration in mid-September.

Caroline decides to go as Elaine the Lily Maid of Astolat; Mick chooses to dress simply as a local fisherboy and borrows some clothes from Petit-Jean.

These riders turn out to be a party of German invaders taking advantage of the fancy dress to gain easy access to the Martello tower.

Nannerl joins the Pony Club, and when Caroline leaves the island she feels Dinah is safe with the German girl until they can return.

Sent to summer school to improve their grades, they dread being cooped up in London, but they soon find Prettyman's Hard, a little community hidden away on the edge of the river in a very old part of the city, which is anything but dull.