In December of 1944, while the Battle of the Bulge rages in the Ardennes, the American 7th Army settles in to what most of its officers and men figure to be a routine and peaceful occupation of the Vosges-Alsace area. The region is mountainous and treacherous, and there are still German forces nearby, but everyone from division intelligence on down figures those forces to have been stripped to support the Ardennes offensive -- everyone except Col. Mark Devlin (Howard Keel), who keeps reminding everyone that the Germans would never leave their forces stretched that thin so near their own border; but his warnings fall on deaf ears. Meanwhile, at the front lines, an infantry platoon finds a woman wounded in the snow. Alexandra Bastegar (Tina Louise) is an Alsatian and speaks all the local languages and dialects, which is more than the American interpreters can do, and she's only too happy to help the people who rescued her -- except that she was shot as a cover and is working on behalf of the Germans. Can Devlin find the proof he needs of a German offensive-in-the-making before Alexandra completes her mission?