The Man Between (1953) on Netflix

Plot summary

Susanne Mallison arrives by air in West Berlin after the war. Her sister-in-law Bettina shows her the war-damaged city and the ruins of the Reichstag, and they spend an evening at a nightclub. The next day the two women go into the eastern sector, showing their papers at a barrier that lifts for them, and buildings there carry posters of Stalin and Walter Ulbricht. In a cafe they meet Ivo Kern. Back in the west, Susanne visits her brother Martin, a British army doctor, and begins to see Ivo, whose associate Halendar keeps appearing.