Eccentric and very British comedy thriller which was started during WWII and completed afterwards, which perhaps accounts for its uneven tone. Eventually the tension gets lost in farce. Deborah Kerr is a haughty Irish teenager who wants to join the IRA but gets exploited instead by Nazi spies on the mainland. Trevor Howard is the bystander who gets swept up in her misadventure.
A problem here is that Kerr's screwball capriciousness rather subverts a serious political stalemate, which was Ireland's neutrality in the war. Consequently the script searches for a balance which it never really finds. It mocks attitudes which were live problems for many.
The girl is portrayed as radicalised. Launder and Gilliat actually create an interesting pastiche of an extremist; the girl has no self-knowledge or sense of humour or nuance. Everything offends her. But mainly the English. And yet the comedy is mostly drawn from this stubborn fanaticism, which feels awkward.
The pacing is slow for a suspense film. But there are laughs in the witty innuendo expertly delivered by the young star. There is stylish noir photography, and more railway locations from Launder and Gilliat, which take the story all over the British Isles. As often with these writer-directors, there's a lot of Hitchcock, but the master might have stayed clear of the political tangle.