It's available in a new print and it looks marvelous. There are a good many great shots in it. Its IMDb rating of 5.9 doesn't do it justice.
Some accurate reviews are on the IMDb site, lauding the film.
The character of the lighthouse keeper was played by Wilfrid Lawson, not an actor well-known to me. But I was very much impressed by the character part and how he carried it off. He does appear in "The Long Voyage Home" (1940), "The Night Has Eyes", "Hell Drivers", which rate a re-watch anyway.
Movita and Michael Rennie play the other two main characters.
This story is set in Germany, off the coast, at a lighthouse. All the Germans are played by British actors with British accents, a bit disconcerting. Rennie is a British spy, we learn early. Movita is an escapee from a Nazi concentration camp.
The lighthouse is occasion for a Hitchcockian sequence or two.