I saw this 52 years ago and was not much impressed then by what I felt was a rather supercilious war report of mostly bombings and fires and a hell endured by a civil population, but this is much more than a war melodrama, as its main character is documentary - it gives a very clear and comprehensive picture of one of the most vital changing points in the war, as Rommel might very well have prevailed at El Alamein of not the bombers of Malta had found and destoyed the convoys of his fuel supplies. It might actually have decided the war or at least been one of the turning points if not the very first one.
There is Alec Guinness, Antony Steel, Jack Hawkins, Muriel Pavlow and others, but the one you will remember is the mother played by Flora Robson with her bleeding heart for her son who went to Italy, chose the wrong side and returned on a spying mission. All her scenes are dramatically the most prominent of the film.
The love story is just an embellishment, while the main film is the documentary of Malta's endurance under a hellstorm, while Flora Robson brings out all the human complexities of the situation, with an inheritance of all the thousands of years when greater powers all fought about Malta, which actually is not much more than a barren desert island, in a tragic position to make it an eternal victim of foreign power struggles...