A mailbox is a magical contraption. From the outside it appears to be no more than a metal box on a pole. But open the door and anything is possible.

A few weeks ago, on a fine sunny afternoon, I opened the door of my mailbox and found a small package from my dear friend, Stuart. I had not been expecting any such package and so was completely mystified. Imagine my astonishment when I unwrapped the package to find a fairy tale, the last book ever written by the poet Randall Jarrell, with wonderful illustrations by Maurice Sendak: a thoroughly enchanting little book that had been out of print for a quarter of a century.

The story begins with a hunter who lives all by himself in a cabin at the edge of the sea. Jarrell manages to describe the loneliness of the hunter in a way that is so simple and clean, so free of bitterness and self-pity, that the story seems to shine.

"In spring the meadow that ran down from the cliff to the beach was all foam-white and sea-blue with flowers; the hunter looked at it and it was beautiful. But when he came home there was no one to tell what he had seen - and if he picked the flowers and brought them home in his hands, there was no one to give them to. And when at evening, past the dark blue shape of a far-off island, the sun sank under the edge of the sea like a red world vanishing, the hunter saw it all, but there was no one to tell what he had seen."

Slowly, carefully, and with the utmost care, the hunter manages to lure a mermaid into his life. She is as strange to him as any woman is to a man, and he is just as strange to her, but somehow they find a way of living together.

Jarrell's mermaid is like a little girl; she is endlessly curious and is surprised again and again by wonders that we land-dwellers take for granted. Her tender relationship with the hunter, at first so tenuous, becomes stronger and surer with each new page.

I will not say what happens next, except that it involves a bear, a lynx, and a boy (in that order). By the story's end, even the oldest and coldest of hearts will be warmer and younger. Like all great fairy tales, this story is as true as it can be.

"Say what you like, but such things do happen - not often, but they do happen."