Her outrageous secret?

Her love for the Viscount!

Meeting dashing Hugh Wilder again at a Society party brings Sylvia's longing to the fore... When she was left shipwrecked on a remote island there was one other survivor: Hugh! Sylvia's never told a soul that until they were rescued they lived and loved as a married couple. Now Hugh's engaged to another. And Sylvia's supposed to be an innocent spinster. But every time they meet her respectable resolve threatens to crumble!