Sunshine on the Mountains — Margaret Malcolm

When Charles Ravenscroft first met Dinah Sherwood, they were both spending a carefree winter sports holiday in the Alps, and his first impression of her was that she was the happiest girl he had ever seen. It was easy to see why -- she was in love with Nicky Gisborne.

Charles' second impression was that there was something not quite right about the situation. But what, after all, did Charles know about it?