Si jeunesse savait...(1948)

Charles Vigne, a wealthy banker, frees Abdul, a good genius imprisoned in a vase. To thank him, Abdul grants his wish: to become a child again, while retaining the experience he has acquired. But the "disappearance" of the banker panics the financial markets and has disastrous consequences for the bank. Eventually, Charles Vigne will ask Abdul to give him back his real age.