The year is early but I’m convinced “45 Years” is one of the best films you’ll see in 2016. It has earned Charlotte Rampling her first Oscar nomination. The voters for the Academy Awards have been going wild about her exceptional work for weeks. When you see her extraordinary intimacy and intelligence on screen, you will understand why.

In the immensely moving drama, Tom Courtenay is Geoff, a childless British retiree soon to host an anniversary gala for his long marriage. He and Kate, his wife of nearly half a century, played by Rampling, will be celebrated by a party of friends toasting the kind, decent duo’s affectionate and contented relationship. They will dance to the Platters’ “Smoke Gets in Your Eyes.” Or, late in life, they will face conflicts lurking in the shadows and the thought that they don’t belong together. That old favorite song is painfully apt.

Like many relationships, writer/director Andrew Haigh’s elegant film starts out lovely then turns grueling. They live in a tidy, book-lined, well-ordered home where he reads Kierkegaard and she makes tea in the kitchen. The director treats them both fondly, giving them a somewhat worn but cozy home where shots that last a bit too long suggest small, ominous cracks beginning to spread.

No sooner does Kate return from a morning dog walk around the couple’s attractive Norfolk Broads home than Geoff shares a surprising letter from Alpine authorities. Half a century back he and an earlier lover, Katya, hiked the Swiss Alps, where she fell through a crack in a glacier and died. Now her ice-encased body has been discovered. It’s a sad memory for Geoff and a reminder to Kate of a small footnote in her husband’s past. Days before their party, Geoff faces a growing sense of pain for a young woman he hardly ever mentions. Kate begins to feel herself plummeting down a fissure in her wintry marriage, a crevasse of frozen emotions and unresolved issues.

What unfolds is a fascinating suspense thriller about human relationships and a tender, stunning mystery. Everything is laid out in plain sight through seamless editing and flawless camerawork. Haigh turns the screw gently and mercilessly, creating a measured, controlled marital drama that can leave you wrecked like “Contempt” or “Away From Her.”

Haigh handles the film’s naturalism like a virtuoso. In one wordless scene, Kate takes advantage of Geoff’s absence to enter the attic as if she were climbing up into Blackbeard’s fortress, where conflict lurks in the shadows. She tours through the past on an old film projector, confronting things she would rather not confront. As it rattles and hums in the dark, youthful passions are revisited with results likely to inspire weeping. In that spellbinding, long single take against the projector’s fluttering light, Rampling tells us the prim and proper Kate’s entire life story.

Her silent reaction makes the home movie’s impact all the more shattering, and Haigh’s film as well. I feel that in the history of movies about love, the restrained, pensive, deeply felt “45 Years” will last a very, very long time.