Matthew Rhys, as Philip, and Alison Wright, as Martha, on “The Americans.”

In last week’s episode of “The Americans,” a woman in a fake marriage—Martha, a secretary at the F.B.I.—began to understand the truth about her life. The surveillance equipment that she had snuck into her workplace, at her husband’s request, had been discovered. Back at home, that husband, “Clark,” a man who was, in reality, Philip Jennings, a Russian spy, began spooling out the usual hypnotic, reassuring spiel about their bright future as soul mates. This was the potent drug that he had used to keep her on the hook for years, despite the fact that he was never around, they lived separately, and he was unwilling to have kids. “If you’re asking me, do you think things will get better?” Philip, as Clark, said, peering through his nerd glasses, “then the answer is yes.”****

As any viewer of “The Americans” knows, the answer to that question is almost certainly no. Martha wasn’t in the mood, she told Clark, for the wine that he was opening—but, really, she meant, for the talk. Her face, downcast, suggested something awful: the anesthesia was wearing off. It was the beginning of the end of a powerful arc about intimacy and betrayal that began two seasons ago. But Martha’s was just one of many plots on “The Americans” that is hard to imagine with a happy ending: there’s the one about the teen-ager Philip is seducing; there’s the one about the recovering alcoholic whom Philip’s wife, Elizabeth, has been befriending, hoping to ensnare her in espionage; there’s the one about their daughter, Paige, an idealistic young Christian, who is being stealthily recruited, by her own mother, to become a spy; there’s the one about their son, an innocent, blind and open to the killers who are raising him. There’s the one about the fate of Philip and Elizabeth’s marriage—a deep bond between two well-trained fakes—and the one about the fate of the Soviet Union itself, which is due to collapse soon, not long after the show’s eighties setting.****

“The Americans” is a bleak show that ends each episode with heartbreak. It’s also a thrilling, moving, clever show about human intimacy—possibly the best current drama out there (at least of the ones I’ve been able to keep up with!). Dread is its specialty and also its curse; it’s what makes “The Americans” at once a must-watch and a hard sell. This is a surprising conundrum because, judging by a plot summary, the series sounds like it should be a fun watch for anyone: it stars two attractive actors, Keri Russell and Matthew Rhys, as married spies with secret lives. By day, they pretend to be mild-mannered travel agents raising kids. By night (and sometimes by day; they have great babysitters), they put on crazy wigs, have sex with other people, participate in complex espionage schemes, and occasionally murder someone. There are memorable “eww” scenes, too, including a brutal sequence of amateur dentistry and another in which a corpse was folded, with alarming realism, into a suitcase. But “The Americans” refuses to do what similar cable shows have done, even some of the good ones: offer a narcotic, adventurous fantasy in which we get to imagine being the smartest person in the room, the only one free to break the rules. Instead, “The Americans” makes the pain linger.****

Is there any other cable drama that, presented with a plot in which a middle-aged man is forced, as Philip has been this season, to seduce a beautiful, eager fifteen-year-old girl, would not make that idea hot, a fantasy for viewers to get off on, even while it allowed us to theoretically disapprove of the idea? Getting a double-message like that across wouldn’t be hard: just paint the girl as a slut or a dummy so that we care a bit less. Age her up a year or two—harden her. Make the situation titillating, make it her fault, don’t make it so upsetting, make it funny, make your antihero better than all other men in the world, so that perhaps it’s actually O.K. for him to have sex with her; maybe those who oppose it are prudes. Or don’t let it really be happening at all; make it just a dream sequence—but, still, use images of her body, to create a nifty fetishistic JPEG. There are many ways to have your transgression and eat it, too.****

Instead, on “The Americans,” we see Kimberly for who she is: needy and callow, but mostly vulnerable, desperate for tenderness and attention—nobody we can simply write off as jailbait. She’s got “daddy issues,” but they’re not an excuse for Philip’s actions; in fact, they make what he’s doing worse. Naturally, Kimberly gets under Philip’s skin, so he keeps trying to put her at a distance, the way you need to in order to exploit a person. As he talks to Elizabeth about what’s happening, he’s alternately contemptuous and tender, protective and dismissive. In a spectacular episode two weeks ago, the two ended up in Kimberly’s father’s empty mansion. Standing on the balcony, stoned, she opened up to him. Her burbling speech—beautifully delivered by Julia Garner—was all skinless bravado. She talked about her dead mother’s garden, where she and her brothers used to plant vegetables. She talked about her father, who was never home, and his new socialite wife, who was also never home. Later, in the gleaming kitchen, the two of them, giggling, with the munchies, mixed Rocky Road and Jiffy Pop, throwing it at one another and giggling. It was a sweet evening; only our deeper knowledge made it a horror show.****

Later, when Phil went home, he seemed drained and depressed. In flashbacks, we saw what he couldn’t help thinking about: the training that both he and Elizabeth had, back in Russia, when he first learned how to pull off this kind of operation. He had been an idealistic teen-ager himself at the time. In those flashbacks, as he slept with strangers, his experience wasn’t portrayed as a sexy fantasy, either, but as a form of institutional abuse: he had been as vulnerable as Kimberly, as plastic as Paige, another kind of mark. Philip talked to his wife about these memories, about how he had learned to “make it real”—to fake intimacy with a stranger until it felt organic. “Do you ‘make it real’ with me?” she asked. “Sometimes,” he confessed, then pulled her close. “Not now.”****

That’s “The Americans” ’s version of a love scene. It’s what makes this season a quiet masterpiece, worth the bleakness it delivers. It’s also what makes it an original show, despite sharing outlines with other action dramas. Many of the most popular antihero shows—even the great ones, like “Breaking Bad” and “The Sopranos”—are about power, about what it means to be the boss. “The Americans” is about loss of control. That’s what intimacy is: when you’re known, you’re in danger. To be loved, you have to be known. In the final scene of last week’s episode, Philip decides to tell Elizabeth a secret that he has been keeping and, as they lie in bed, spooning, it seems likely that he’s making a terrible mistake. The more she knows, the more she has to use against him. But, like Kimberly, he can’t help it. He has to believe that it's real.