Neither Five Nor Three — Helen MacInnes

Nothing in Rona Metford's chic, sophisticated world of publishers, writers, and artists warned her of the sinister web of terror and treason that was slowly winding itself around her. But the insidious evil lurking just beneath the surface of her love affair with an ambitious young journalist could not stay hidden forever. Strange events and stranger friends suddenly triggered off an explosion that plunged Rona into the very center of a violent and dangerous conspiracy.