Mystery Island — Ethel M. Comins

It really seemed as if Marjorie Gardiner's lifelong dream was coming true at last! An island all her very own. Where she could spend glorious days pursuing her goal of becoming an historical novelist. And all this would be possible if she could fulfill the odd condition of her second cousin's will Milton Heath had left Maple Island -- now dubbed Mystery Island -- to Marjorie with the stipulation that she most live on it -- alone -- for eight consecutive weeks before she could claim her inheritance.

To Marjorie this presented no problem, but Gus Sheldon. The young insurance man to whom she was practically engaged, strongly opposed such an arrangement. After all, who knew what plight might befall a young girl living alone on a deserted island? And to complicate matters, Marjorie's younger sister, Amber, declared that since nothing had been left to her, she was going off to New York to try her hand at modeling.

Marjorie bore both with Amber's defection and Gus's pleas, and ignoring the tentative warnings of John Robinson, the lawyer who had presented the will, she set off for Mystery Island undaunted. She was lucky to find a friendly neighbor in red-bearded Brock Cameron, who was summering across the water on Eagle's Nest -- especially after she discovered that someone was desperately trying to prevent her from maintaining her necessary residency. But who would want her off the island--and why?