Savage kept himself going in a Japanese prison camp by fantasizing about Maria, and now wants her very, very badly. It doesn't take Maria long to realize that she is really in love with him. But Savage loves Maria too much, and the trauma of the prison camp, particularly an experience involving a rat, spilled over into his fantasy life with Maria. The intensity of his love and the problems caused by his nightmares and fears begin to destroy their life. I hesitate to get into too many specifics, not because the plot goes through very surprising twists, but because telling too much could cause further impatience with the film's fairly slow pace.
Events happen quickly, but themes and resolutions develop slowly.
John Savage has the centerpiece role in the film, despite the title, and it's the best role he has ever had, offering him many opportunities to portray his character's passions and frustrations. His performance overshadows solid work from the rest of the cast. Nastassja Kinski, for me at least, always seems to carry around an slight aura of both perversion and perversity. She tones this down, but doesn't completely eliminate it, in her role as Maria. While she is very strong in the part, it might have been better served by a more classically All-American girl.