Loosely based on a couple of Somerset Maugham's Ashenden stories; three British operatives are detailed to assassinate a German agent before he leaves to meet contacts in the middle east in a politically troubled Europe readying itself for WWII.
It is another Hitchcock comedy thriller, but with a sliver of moral deliberation on war and espionage. There's a particularly great moment of visual storytelling in the murder of the wrong man by Peter Lorre on a mountain, viewed distantly by a morally disavowing John Gielgud through a telescope.
The main debit is a rather disinterested display from Gielgud who mysteriously fails to shine in the reflection of another feisty performance from a stunning Madeleine Carroll. The German double agent played by Robert Young shares far more chemistry with her.
It's fine Hitchcockian entertainment, with inventive use of sound, invigorating visual set pieces, and many thrilling moments, particularly at the climax as the train leaves Switzerland, exposing the British spies to danger without the protection of neutrality.