The Promise by Danielle Steel

Young architect Micheal Hillyard and artist Nancy McAllister are determined to get married despite his wealthy mother's disapproval. Then minutes before their wedding, a terrifying accident and a cruel deception separate Micheal and Nancy--perhaps forever. Each pursues a new life--Nancy in California, Micheal in New York. But eventually nothing--and no one--can keep them apart as they keep their vow never to say good-bye.
 
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