Ethel Lina White 
Step in the Dark [EPUB ebook] 

She Had Everything To Fear. Suddenly beautiful Georgia Yeo realized that she was not the guest of her fiance, Count Gustav, on his lonely Swedish island — but his prisoner! Her terror was not for herself alone. She had brought her two young children to the island. And now Count Gustav threatened their lives if Georgia refused to help him in a gigantic swindle. There was only one small chance to escape that island and Georgia had to take it. As she made her plans, she dared not betray to the Count the fear she felt.