1943, The Netherlands is under total Nazi occupation. In Amsterdam, Jack, an unassuming accountant, first meets Ina at a birthday party - a 20-year-old beauty from a wealthy diamond manufacturing family who instantly steals his heart. But Jack's pursuit of love will be complicated; he is poor and married to Manja, a flirtatious and mercurial spouse. When the Jews are being deported, the husband, the wife and the lover find themselves at the same concentration camp; actually living in the same barracks. When Jack's wife objects to the "girlfriend" in spite of their unhappy marriage, Jack and Ina resort to writing secret love letters, which sustain them throughout the horrible circumstances of the war.