The film, which opens this week, is set in London during World War II. Fiennes plays a moody novelist, Maurice Bendrix, caught in a triangle with a beautiful woman (Julianne Moore) who’s married to a boring civil servant (the outstanding Stephen Rea). When she breaks off their intensely hot affair, Bendrix grows even more obsessed with her. “He’s got a cruel streak,” said the actor. “But then you kind of warm to him, because–as Neil says–his hatred and anger is all because he’s desperately in love.” Fiennes has been called a “cold” actor, but that’s not really fair: it’s just that he’s so good at expressing deeply buried emotions, eloquently telegraphing the subtlest of feelings across his face. In the film “Onegin,” opening just before Christmas, Fiennes once more shows off this gift. Pushkin’s world-weary Russian aristocrat is a vastly different character from Bendrix, but he’s also a man surprised by the power of love, and ultimately broken by it.

“Onegin” was a family affair: Fiennes’s sister Martha, in a remarkable debut, directed the lavishly beautiful film, and his brother Magnus composed the original music. (Three other siblings include the actor Joseph and his twin, Jacob, who’s a gamekeeper in Norfolk.) Their parents were artistic, especially his mother, who was a novelist and painter. Ralph himself started at art school, before switching to acting.

Fiennes, 36, just back from a trip to Tokyo to promote “Onegin,” sipped green tea during the interview and talked about performing “Richard II” and “Coriolanus” in repertory next year in London. He’s polite and a bit reserved, choosing his words with care. On the ring finger of one elegant hand, he wore three slender gold rings. (He denied he’d married–as an English tab rumored–his companion, actress Francesca Annis.) The talk turned to a movie he’d seen that he especially liked. " ‘The Blair Witch Project’!" he said, with a small, wry grin. “I really loved it.”