Because sometimes, the most powerful love story is the one that never begins.

Then there is the music. Nat King Cole’s "Quizás, Quizás, Quizás" (Perhaps, Perhaps, Perhaps). A waltz by Shigeru Umebayashi. Every time the melody swells, you know something will not happen. The music is the sound of longing converted to regret. Why don’t they just be together?

So pour a glass of something amber. Turn off the lights. Watch two of the greatest actors who have ever lived do absolutely nothing except exist near each other. You will feel your own ribs tighten.

They rehearse scenes. "How did it start?" they ask each other, pretending to be the cheating partners. They eat noodles alone in cramped rooms. They leave each other’s apartments without being seen. They rent a room together to write martial arts serials—but always with the door open.

But Wong Kar-wai is making a film about decency as tragedy. Mr. Chow and Mrs. Chan cannot commit adultery because that would make them equal to the people who betrayed them. They hold onto their pain like a moral shield. They would rather be lonely than be wrong.

If you have never seen it, you likely know its image: Tony Leung Chiu-wai in a crisp, tailored suit; Maggie Cheung in a high-collared cheongsam so tight she can barely climb the stairs; the two of them passing in a narrow Hong Kong hallway, drenched in red neon rain. The film is a vibe before we had a word for it. But to reduce it to aesthetic is to miss the wound at its center. Mr. Chow (Leung) and Mrs. Chan (Cheung) discover their spouses are having an affair. That is the engine. But Wong Kar-wai is not interested in the affair itself. He is interested in what happens next: two lonely, honorable people trying not to become the thing they hate.