Keith Stewart is a quiet and unassuming man called upon to undertake an extraordinary task. A skilled maker of miniature working models, he lives a modest life devoted to his hobby. But when his sister and her wealthy husband die in a shipwreck on a coral reef in the Pacific—while trying to smuggle out of England their entire fortune in diamonds hidden in the keel of their yacht—Keith becomes trustee for his orphaned niece. To save her from destitution he must travel halfway around the world and risk a long voyage in a small boat in inhospitable waters to recover her inheritance. In the course of his adventure-filled quest, a colorful and international cast of characters mobilize to help him, and this humble man discovers he has more friends and admirers than he could have dared to imagine.