Apparently this was made into a film in 1943blurb - Frances and Richard Myles are newlyweds honeymooning in Europe on the eve of World War II. Unexpectedly, they find themselves commissioned by the British secret service to secure the plans for a new secret weapon masterminded by the Nazis (involving magnetic mines). The trail leads them to Innsbruck where they arouse the suspicions of Gestapo chief Von Aschenhausen. Having secured the plans, the couple find great difficulty leaving the country. Frances is captured and held in a remote castle. She is rescued by her husband and a group of British agents, and, using underground routes, the couple finally cross the border to safety.