Someone else unfortunately used the title, location, location, location, in his film review. It's not only the plot of the movie, it's the history of Malta.
Malta located south of Sicily and right in the middle of that Mediterranean bottleneck between Sicily and Tunisia has had the misfortune by geography to be smack in the middle of supply and trade routes since ancient times. That made it desirable real estate. Malta's been occupied by every conqueror operating in that area, most recently the British during World War II.
And at that time that island with its air and naval base was doing a lot of damage to Erwin Rommel's supply route in North Africa. With unbelievable courage the British garrison held on for over two years and was never really out of harm's way until the Allies took Sicily.
Lots of black and white combat footage used and together with the performances of the male leads, Alec Guinness, Jack Hawkins, and Anthony Steel the film has a nice documentary feel. Guinness who plays so many quirky type characters on the screen is for once a very straightforward lead as Peter Ross aerial reconnaissance photographer. He has a romance going with one of the locals and her mother is played by Flora Robson.
There is an interesting subplot there in which Flora Robson's son is taken prisoner as a spy for the Italians and sentenced to be executed as a spy. He tells his British captors that he is in fact a Maltese patriot and that they are the occupiers and it's their occupation that is bringing death and destruction to his people. Not that he wasn't right. The Maltese finally do have their independence now.
A film that is a great tribute to the heroism of the British forces on the island of Malta.