An army platoon, supposedly on manoeuvres, arrives in the town and is at first welcomed by the villagers. But they are in fact an undercover Nazi regiment, preparing the way for a full-scale invasion under the knowing jurisdiction of the quisling local squire (Leslie Banks, superb as always). When eventually they are exposed and forced to take the whole village hostage, some of the villagers attempt a desperate resistance.
At this point, the doom-laden tension so carefully maintained throughout the film gives way to some quite unexpectedly explicit violence - including a shocking killing with an axe and a scene in which a woman allows herself to be blown up by a hand grenade so as to save a room full of children - that seems all the more brutal in so idyllically English a setting. As in real life, characters are killed more or less at random as circumstances dictate, in ways both heroic and banal, regardless of their likeability or centrality to the plot. Which, obviously, was the whole point of the enterprise.
Ironically, the release of the film was delayed by a year over concerns that such factors may prove counterproductively harrowing, inducing panic rather than preparedness. (It certainly belies Ealing’s habitual reputation for gentility.) Now, without such imperatives to consider, the film can be seen more clearly as the exceptional piece of work it always was, while its durability and power may be indicated by the fact that its central idea reappears in both The Eagle Has Landed (1976) and the film version of Dad’s Army (1971).