Tom Courtenay and Charlotte Rampling

Kate and Geoff Mercer (Charlotte Rampling and Tom Courtenay) have spent most of their lives together; having weathered their share of adversity, including Geoff’s heart attack a few years back, these retired spouses aren’t easily fazed. But at the start of Andrew Haigh’s stellar drama 45 Years, they learn that the body of Geoff’s former girlfriend, Katya, has been found on the Swiss mountainside where she perished in a 1962 hiking accident. Geoff told Kate about the tragedy decades earlier, and the dead lover has receded in their memories. But now the snow over the glacier crevasse where she was entombed has melted, revealing her perfectly preserved. Climate change is particularly appropriate as a plot device here: the receding glacier exposes not only the corpse but also nagging doubts and messy emotions, just in time for the Mercers’ upcoming 45th wedding anniversary.

Theirs has been an enviable union: their closeness, forged over nearly half a century of intimacy and interdependence, has bred a near-effortless synchronicity. Their comfort with each other reinforces their nurturing, and vice versa. Their modest country house in England’s misty Norfolk Broads wetlands is cozy, not stifling; companionable dogs have filled the space of the children the couple never had.

Rather like dancing, a good, long marriage depends on balance and rhythm. Two people step together in a certain direction, but then sometimes separate with a little twirl for a brief solo before reuniting. In the Mercer household, Kate is the early riser. By 7:30 on any given morning she’s back from walking the dog, removes her coat and muddy shoes, drinks a glass of water in the kitchen, where Geoff sits over breakfast, and then they chat about the day ahead. She cleans up after him, but he does the heftier chores. She takes the car into town for errands while he stays behind to fix the plumbing. When he cuts his finger, she bandages him. They’re both retired—he was a manager at a big plant, she used to be a schoolteacher—so their talk over dinner centers on their friends and social calendar. Then it’s time for some TV or reading before they head up to bed, undress, talk a bit more, and sleep.

This is their routine, and it has served them well. Everything has its place in a marriage based on such sharing and communication, so much so that once Kate hears disturbing new details about Katya, the Mercers are headed for their own fall. The incursion of the unknown erodes their domesticity, and the things that have made their marriage strong—intimacy, synchronous rituals, and the interdependence that comes from mutual caring and respect—turn it into a minefield.

The problems begin with Geoff, so abruptly sideswiped by grief. The Swiss authorities have contacted him as Katya’s next of kin—as he reveals to Kate, he and Katya posed as married so they could bunk together in people’s homes. This fairly innocuous admission upsets Kate, as does Geoff’s response to his own agitation: “Don’t be cross, Kate, I’m going out for a smoke.” His smoking becomes more frequent; returning home at one point, she opens a window, gently chiding, “I don’t want us to start smoking again.” They gave up smoking together, and not only is his resumption of the habit dangerous for his heart, it’s breaking their pact. Geoff is also mulling over the Swiss authorities’ suggestion that he return to the Alps, presumably to identify Katya’s body. “You aren’t thinking of going?” Kate asks in horror. “You don’t even want to go for a walk with me on the Broads, and that’s as flat as a pancake.”

The growing friction between them comes out in surprising ways. Geoff becomes obsessed with climate change, and he goes to the town library to check out a book on the subject, which makes him late for his lunch with Kate. When their best friends spot them through the cafe window, Kate urges him to hide the book, as if it’s some dirty secret. Later these same friends unwittingly prompt an argument by urging Kate to get Geoff to attend a reunion with his old work colleagues. “You can’t just back out of things, even if you have reasons,” Kate insists. Geoff grudgingly relents, and their synchronicity is restored, but on the drive home from the reunion, his stomach turns.

Other fissures in their once perfect life appear, such as Kate’s casual observation that there are no personal photos around their house. But none is as damaging as the way Geoff abuses their intimacy by turning their late-night chats into ruminations about his lost love. Jealousy and resentment over a long-ago predecessor may be illogical, but bringing the specter of the dead woman into their bedroom every night is too much sharing for Kate. She begins to wonder who she really married, especially now that Geoff seems to be disappearing before her eyes—quite literally, as he sneaks up to the attic to gaze at old slides of Katya.

After Kate orders Geoff to get a grip, he snaps out of his doldrums. He renews his attentions to Kate, goes on a nature walk with her and the dog, and buys her an anniversary gift. You’d think she’d be grateful for these signs of returning normalcy, but the recent revelations about his individuality have wrecked her sense of marital security. Did Geoff’s reticence about his earlier life constitute lying, or was he merely being protective of her feelings? And if she can’t be everything to him, does that mean she is nothing?

In Geoff’s eagerness to please Kate, he doesn’t see that he has done something she can’t forgive: he’s had a past, a chunk of time, beautiful but fleeting, in which she had no part. As he gamely leads her to the dance floor at their party, where they and their guests sway to the strains of “Smoke Gets in Your Eyes,” the Mercers’ respective follies border on tragedy, spinning an end to this cautionary tale. To know is not the same as to possess, and at any rate, possession is never permanent.