The Dangerous Islands — Ann Bridge

Julia Probyn-an old friend of many readers-is sailing off the west coast of Scotland. On the desolate island of Erinish Beg, she and her cousin are startled to see a sky-blue pole rise up out of the ground at their feet. Military Intelligence sends Colonel Jamieson to investigate this find. The action moves from the Erinishes to a tweed-shop in Tobermory, an archaeological dig on Lewis, an island off the County Mayo, and finally to a dramatic end in the Scillies. The mystery of the sky-blue pole is solved soon enough; but there is much journeying, heart-searching and danger for Julia before the whole system of espionage is laid bare. During these events Julia, more and more attracted to Colonel Jamieson, finds in him the man she will marry.