Misty of Chincoteague by Marguerite Henry

Have you ever wanted anything so badly that you knew your heart would break if you didn't have it?

That's the way Paul and Maureen feel about the Phantom, one of the wild ponies on Assateague Island. She's a beautiful copper and silver pony with a white map of the United States over her shoulders. Every year, the people of Chincoteague Island hold a Pony Penning Day, rounding up the wild ponies, but every year the Phantom has escaped the round up.

This year, though, it's going to be different. Paul's old enough to help with the round up, and he's determined to bring the Phantom in. And when he does, the brother and sister are going to buy the Phantom and give her a good home - her and her little silver-gold colt, Misty.

The siblings have hard work and a lot to learn along the way: they have to save up the Phantom's hundred-dollar price, deal with the highs and lows of the Pony Penning Day, and then, if they're very lucky, win the trust and cooperation of an independent, tough, thoroughly untamed pony.