Stars Debra Winger and Tracy Letts give a master class in subtle performance in “The Lovers.” As an unhappy husband and wife, each planning to end the marriage in favor of their respective lovers, they tell so much of their stories through their faces in close-up. Summer blockbusters have their place, but this one will knock your socks off — quietly, because it feels so real.

Mary (Winger) is having an affair with a chain-smoking writer, played by Aidan Gillen (Littlefinger in “Game of Thrones”) and her husband Michael (Letts) is having an affair with a volatile ballerina (Really, is there any other kind?), played by Melora Walters. While both of these illicit partners have more romantic careers and are younger, Mary and Michael spend their days chained to their respective cubicles. “The Lovers” takes its time showing us their lives, but rather than a scathing indictment of the much-maligned suburbs, it’s a matter-of-fact view of life that isn’t played for bitter laughs, merely shown realistically.

Even the affairs are shown in the cold light of day, not as stolen moments of pure bliss. Both the writer and the ballerina are demanding and petulant, and at one point Michael pretends to meet a friend for drinks and lies about it to both his wife and his girlfriend. The film and the performances are dramatic but not showy; it’s a story of middle class boredom we’ve heard before, but through a lens of reality that dignifies rather than mocks it.

As the married couple awaits a visit from their touchy college-age son, they assure their longtime lovers his visit will be the turning point, after which they will be free from their marriage. He is the only thing keeping the couple together, and placating him is their stated goal. Meanwhile, the son simmers with resentment over his parents’ loveless union.

Then one morning, in the week of preparations for his visit, the marriage stops being loveless. Again, Winger’s face in close-up, registering a range of emotions, beats any special effect you will see this summer. While the thrill of the illicit ignites their feelings for one another, you also get the sense that it is the familiarity between Mary and Michael that has suddenly been remembered to be a huge part of their connection. The film’s most touching scene is in the grocery store, when Michael is made to realize what he would really be losing in giving up his marriage.

Slowly, the stakes in their marriage become high; their divorce, once a foregone conclusion, is now something to mourn, or avoid. The rage in their already insecure and impatient lovers when they realize what’s going on causes them to strike out. Any histrionics come from these long-suffering sideline affairs, or from the son himself. The greatest contrast the film makes ends up being between the older couple, and the younger people they upset.

Bittersweet and truly suspenseful, “The Lovers” is a story almost like a Nancy Meyers romantic comedy, but the romance is almost painfully real, and the comedy far more measured. Even while the setup of their story is unusual, the scenes from a marriage are realistic, and will probably hit home with anyone who has been married, however happily, for any length of time. These actors have vividly made a normal life a complex and unpredictable thing to see onscreen.

“The Lovers” is now playing at the Crescent Theater.