SPOILER ALERT: Do not read until you’ve watched the series finale of “The Americans.”

From the beginning, “The Americans” was a show about two people trying to pull off a balancing act at a precarious time in history — playing at being a typical suburban family while maintaining a complicated loyalty to the USSR. In the show’s final episode, the ruse fell apart — and, in a twist, Mother Russia won out over real-life family ties. Philip and Elizabeth Jennings managed to survive the episode by fleeing back home to a Russia they barely recognize, in the process abandoning their son and getting abandoned by their daughter. That they survived a show that seemed set on killing them surely surprised many fans; that the final moments we share with them is spent in grim contemplation of a life of isolation and regret was, in the end, no surprise at all.

In the run-up to this episode, the walls had seemed to be closing in on the Jennings, as Stan Beeman had moved from suspicion to near-certainty that his neighbors were subverting the state, and Elizabeth had definitively broken with the Centre that had given her and her husband orders for the show’s entire run. With their most concrete existential threat to date and no one left to give them orders, Philip and Elizabeth were, suddenly, entirely improvising. A debate early in the episode about what is to be done with Henry — ”His future is here,” says Philip — sets the tone. For seasons, the show’s spies have existed in the uneasy understanding that tough conversations would happen someday, and have pushed them off. They’d finally arrived.

Henry was hardly a pivotal character, but his abandonment represents the show’s mercilessness with Philip and Elizabeth. It’s almost certainly the “right” decision to have left Henry in the only place he’s ever known as home rather than escaping with him to the Soviet Union, but, in making it, both parents show off their character defects — Philip’s lack of courage masquerading as a sort of pragmatic humanism, Elizabeth’s grim determination even to plans she doesn’t quite understand. (“We cannot take him!” Elizabeth practically spits at daughter Paige, later, having fully committed to a plan she’d rejected at first.) That we can be quite this engaged with characters this challenging is part of “The Americans’” genius.

Part of why we root for them is because their problematic qualities make them so marvelously good at their jobs — “The Americans” was perhaps the most developed yet version of the TV trope of the antihero whose failings fuel his or her genius, in part because it had two antiheroes whose flaws and whose gifts complement each other. Watching Philip and Elizabeth operate together on Stan as he corners them in a parking garage feels like a parting gift from the show, a last glimpse at two virtuosos working in harmony. “It’s all over,” Stan intones, with gun pulled — but it isn’t, as the two spies manage to prey on Stan’s weaknesses and insecurities in order to escape with their lives.

That outcome is deeply in doubt throughout, though; a show in which the mission takes importance over all else is one in which to Philip, even Elizabeth might have been expendable. (The reverse seems yet more true.) In the end, though, Philip and Elizabeth were loyal to one another above all else; the cyanide capsule that had haunted the season, dangling around Elizabeth’s neck and over all of the characters’ heads, was casually discarded, a stroke of particularly sharp storytelling. Elizabeth, once willing even to die in service of her country, had lost that animating passion; whatever her life would be like after her mission in America had ended, she wanted to live.

Viewers had long sensed, though, that something huge was stalking the family; this story couldn’t end well. And in the end it wasn’t death but family fracturing that provided the show’s last huge twist, as Paige, the daughter who’d known her parents were spies and who’d begun to pitch in on tradecraft, ultimately jumped ship, sneaking off the train her family was taking to Canada just before the border. Her engagement with the cause had always been, unlike her parents, a utopian one; Philip resented the mission and Elizabeth threw herself into it, but for both of them, it was a job. For Paige, whose passion for social justice her parents knew how to flatter, it was an opportunity to make the world a bit better. But a world in which her brother could be ditched at boarding school while her parents fled to Russia wasn’t a better one. Neither was one in which her goodbye to her parents would be communicated in a silent look from a train platform, but it would have to do.

As much as any other show since, say, “Breaking Bad,” “The Americans” needed to stick its landing, and it did so with a brio that cements it as among the defining shows of this decade. The show was racing against a ticking clock of history that ended with the dissolution of the Soviet Union; we knew the Jennings’ mission would end, and not in triumph. Their act grew harder to carry off each season, and, among fans, wondering quite how it would ultimately fall apart was a parlor game of sorts. That the show kept both spies alive felt true to what we knew of their abilities and their commitment to one another. That their staying alive ultimately estranged them from their children provided a painful, beautiful moment of character study, as both simply try to endure. They’ve never been good at talking about their feelings; they’re not American, and it’s not how they were raised. And so in the show’s final moments, they stare onto a landscape they haven’t known for decades and vow to just keep on going. “We’ll get used to it,” Elizabeth intones, in Russian.

The final season of “The Americans” featured series-best acting by its two leads (both of whom should find themselves among the frontrunners come Emmy time) and a renewed sense of purpose; while Season 5 had been better than most else on the air and a necessary seeding of certain plot elements, its slow motion sapped a bit of the show’s momentum. By contrast, the final season literalized the show’s race against time, zooming through story with increasing danger and anguish. Neither Philip nor Elizabeth seemed to recognize themselves in the final season; the demands of their work had made their front as an American family untenably uncomfortable. It was easier to be Americans than to be spies; in the end, they were forced to choose the latter, and left behind their children as just another element of a now-discarded alias. Finally stripped of those covers and free to be themselves, they don’t know where to begin. They stand together, but oddly apart, staring out on a city that, to them, seems at once foreign and home.