5 children leave London, as their father is at war, while their mother is busy treating the wounded on the front. Their destination is a house on the sea where their uncle lives, with whom they will spend the summer holidays. Immediately the uncle proves very strict, as he wants absolute silence, because he is writing a book. Here they will also meet the housekeeper Martha, nice but a bit crazy and their cousin Horace, a child who has a passion for science and has built a small laboratory in the basement. As they walk around the house, the 5 children discover a secret passage, under their uncle's house, which leads them to an unknown beach. Suddenly the boring vacation turns into a wonderful adventure as, digging in the sand, they find an old elf buried for 8.000 years, named Psammead, the last sand elf in the world. As a token of thanks, the elf asks to make their wish come true by sunset. The children are in seventh heaven, but they soon realize how difficult it is to have to choose a single desire each from the many that they would like to fulfill. Their wildest wishes can cause a lot of trouble: stopping cars, summoning dinosaurs, growing magical wings, but which will be the most important?

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