Ronnie flung down his towel and burst out, "Aunt Marthy, isn't a broken promise the wickedest thing on earth?"

Martha Morse took her hands out of the water and gave the question her full attention. "I don't believe so," she said gravely at last. "It seems to me I can think of wickeder things. I guess cruelty -- hurting anything little or defenseless -- is my idea of the worst kind of wickedness. Still, I can remember when I'd have agreed with you," she added honestly. "But you get used to broken promises, Ronnie. Broken promises, along with good intentions that have gone wrong, just litter the highway all through your life. They're nothing to bother about much unless they're your own. But they're mean, Ronnie. A man who breaks a promise has a weak place in his net. Sometimes he'll get by with it. but sometime he'll lose the catch of a lifetime. But we've got to remember one thing before we dare to judge Byron Flagg or anyone else -- we've got to know why he broke his promise. Maybe he had a good reason."

Ronnie showed no interest in Byron Flagg's reason, but he said fiercely as he picked up his towel again, "I'll never break a promise as long as I liive!"

Martha Morse made no comment, but she thought to herself, "If he can live up to that, he'll be in debt to Byron Flagg."

Ronnie and his aunt take care of the lighthouse while the keeper is on vacation, and when he does not return as expected, they discover that Tern Rock is a perfect place to spend Christmas.