What do you do when you find out the love of your life chose you as a backup plan? What do you do when you find this out a week before your huge 45th anniversary celebration? Such is the concept at the core of 45 Years, the new film from Weekend writer/director Andrew Haigh. The woman at the center is Kate Mercer (Charlotte Rampling), who has been married to her husband Geoff (Tom Courtenay) for this lifetime with hardly a blip along the road. After their 40th anniversary celebration was postponed due to her husband’s bypass surgery, Kate is all set to begin final preparation for the 45th when her husband receives a letter informing him his old companion and lover’s body was found perfectly preserved in the glacier into which she fell over fifty years ago. This seemingly innocuous event dredges up a wealth of feelings in both Kate and Geoff that sends their week into chaos.

There are two ways this film could have been made, and Haigh shrewdly chooses to frame 45 Years from the perspective of Kate. The beauty of this decision lies in the obfuscation of feeling that comes from experiencing the event from the outside. Kate has no frame of reference for this new information, and as Geoff slowly reveals more details in passing (first that he was considering going to Switzerland to see the body, second that he was considered her next of kin because they were pretending to be married and so on), the security and sanctity of their marriage begins to crack. It all plays out in Charlotte Rampling’s eyes and body language, the way she slowly evolves from warm and inviting to colder and distant the more it becomes clear (to her at least) that she’s more of a replacement to Geoff than her own woman.

It is in this aspect of the film that 45 Years makes itself so enthralling. It generally feels like so many independent British dramas we’ve seen before, but Haigh expertly injects this specter of a long gone woman who hangs so heavily and oppressively and oppositely on the hearts and minds of his two main characters, making its cinematic relative closer to Hitchcock’s Rebecca than the modern evolution of quiet stage plays and costume dramas. There is an undercurrent of paranoia that skates along beneath the surface of their relationship, growing in intensity as the film pushes inexorably toward the party that is supposed to represent the strength of their now shattered relationship. 45 Years is not as arch as Rebecca was; there are no characters remotely like Judith Anderson’s Mrs. Danvers, but that sense that the ghost of a lost love is lurking in the corner of every scene.

Rampling is the film’s star and offers one of the better lead performances in a year almost comically stacked with enough dazzling female lead roles to choke a whole herd of horses, expertly calibrating her emotions throughout the rollercoaster of a week. She conveys so much without need of a single word, pulling from a deep well of sadness and weariness, the weight of a 45 year relationship disintegrating before her eyes. Her work culminates with two devastating scenes in the film’s second half, one of them in private and the other uncompromisingly public. It is in these moments that Rampling elevates both her character and the film to new heights. She gets to the core of the human condition, of the misery of being someone’s second choice, of the transience of relationships. She is the sort of actress who is not particularly well known among mainstream filmgoers (her run on Dexter is likely her most well known role to this date), but hopefully the recognition she is receiving for 45 Years and the awards consideration she will almost certainly get will change that tune.

This is not to belittle the work of her partner in crime Tom Courtenay, who is more of a support than a lead but has plenty of opportunities to prove his worth as an actor. His performance is all about genial oblivion, never cognizant of what he has done to his wife until they are well past the point of no return, casually dropping information about his long dead lover like it is not torturing the life partner standing in front of him. Haigh knows exactly what he needs to get out of Geoff as a character, and Courtenay is more than happy to oblige. Thanks to Rampling and Courtenay, 45 Years is a heartrending experience not to be missed.