The plot develops with just enough direction and character development to keep a general story in focus. Seemingly standard inter-war spy movie with a beautiful female spy, threatening German spies, murder, and clean cut British agents. The cast is good with Vivien Leigh and Conrad Veidt playing their roles well. The supporting cast is like many early movies, lots of professionals with good craftwork and little fame. The production is interesting look at the period and the state of movie making. The special effects are simple, but effective for their period. Obviously, in a British film the star will be pure in the end, and can not be a German agent. However, Leigh does a good job of keeping the real situation under wraps for a while. The characters take on depth, but most drop away by the end. Only the main spies from two sides are left in the center, and the romance overcomes the effects of the war. Probably during WW2, the British film industry reflected differently on the end of the movie, but it was in the can. An interesting film: fun to watch Leigh and Veidt, and a good period piece on the politics, morays, and society in neutral Sweden in WWI.