This 1940 British movie was an unabashed propaganda effort, one primary goal was to lure American into WW2. Not a bad try!
As the movie opens, the German U-boat U-37 has just sunk a cargo ship off the coast of Canada. Some survivors clamber up onto the sub's deck, but they're shoved right back off again. Damn Nazis. (Although I have to admit, I'm not sure how Allied subs would have handled the same situation.)
On the run from patrols, the boat decides to hide out in Hudson Bay. A small group of six is sent ashore to seek provisions and… kaboom, the sub gets blown out of the water.
So now what do those six guys do? Well, first thing is to make it to a fur trading post, where they encounter—I am not making this up—Sir Laurence Olivier, playing a trapper with a Quebecois accent that probably would get him in big trouble in modern Canada.
That encounter turns bad, for both Canadians and Nazis. So the Nazis move on, and on, encountering various Canadians along the way. The major problem is that they can't shut up about their vile ideology, keep getting discovered, getting into violent deadly scrapes, and then moving on.
It's all pretty good, in a 1940s way. Famous actors Leslie Howard and Raymond Massey play Canadian civilians that the Nazis encounter, to their dismay.