Previously on “The Americans” (FX), the K.G.B. sleeper agents Philip and Elizabeth Jennings sought to undermine the American empire, and succeeded—as characters created by Joe Weisberg—in demolishing distinctions between the domestic drama and the international thriller. (Warning: this piece will contain spoilers aplenty.) The events of the fifth season ended in 1984, with the husband (Matthew Rhys) quitting the spy game. At the beginning of the final season (which premières tonight), set in 1987, he has fully become Philip Jennings, who operates Dupont Circle Travel with the ambition of a good bourgeois. Meanwhile, his wife, Elizabeth (Keri Russell), is still spying, and she’s become no one at all. It’s not exactly true that Philip has come in from the cold, but it’s clear that Elizabeth is the cold itself.

Bitterly shivering at her own essence, she gives the appearance of being homeless in her own body. Philip frowns acutely while Elizabeth smokes many more cigarettes than usual, staring nowhere, hunched and hugging herself for stability. Scraped raw by her job, sustained by a talent for brutality and a trust in the culture of Mother Russia, she is strung out, impatient to the point of operational sloppiness. One early murder, though conceivably defensible as a standard procedure, nonetheless has the tenor of a thrill kill. Her daughter, Paige (Holly Taylor), remains committed to becoming a sleeper agent herself. Thus, Elizabeth’s parenting now combines cultivating a predator and grooming a victim. When Paige, who’s been doing independent reading on the spy trade, asks whether honeypots are really a thing, Elizabeth tells an assuaging lie. A mother’s work is never done.

It is the eve of a summit meeting between Ronald Reagan and Mikhail Gorbachev. Soviet officials have come to town to discuss a nuclear-disarmament treaty, and Elizabeth is assuming the disguises of her craft—the masks under which her face went missing—at a violent pace. Beneath a frizzy wig, she impersonates a home nurse for the wife of an American negotiator; behind foxy, blocky spectacles, she bats eyelashes at a bureaucrat to gain gossip from Foggy Bottom; styled as a bohemian traveller, she goes to Mexico on a hard-core, deep-state deal. A faction of Soviets believes that Gorbachev might negotiate away an apocalyptic gizmo still in development—one that would annihilate the United States if the Soviet Union were already destroyed in a nuclear attack. Would Elizabeth please keep an eye on Gorby’s favorite foreign-affairs officer? So that the military can stage a coup, or what have you, if need be? The military man who inveigles Elizabeth on this count gives her a jewelry box, containing a pendant necklace. The pendant contains a suicide pill, maybe; “The Americans,” menacing as ever in its reserve, won’t spell out whether it’s a charmed totem or a cursed amulet.

This turn of affairs stimulates a return to America by the former K.G.B. agent Oleg Burov (Costa Ronin), who leaves a cozy life in Moscow to urge Philip to watch Elizabeth. In turn, the F.B.I. agent Stan Beeman (Noah Emmerich), who had quit counterterrorism for a quiet life investigating homicides, receives the assignment of checking in on Oleg. Thus does the show get the band back together, with a keenly felt sense of summation.

Does Philip have the stomach for this sort of domestic disturbance? His new posture around the house is that of a worried man eating a lonely sandwich at the kitchen island. He has thrown himself into work too aggressively, expanding his office to the detriment of his cash flow. The financial situation somewhat disturbs the bursar’s office at the boarding school where his son, Henry (Keidrich Sellati), has enrolled, either because his parents wanted to support his dreams or because the writers’ room needed a place to shunt him. Endeavoring to motivate his employees, Phillip plucks a book from his office shelf—“Success Through a Positive Mental Attitude,” a self-actualization manual first published in 1960—and is inspired to deliver a rousing speech to his embarrassed office. His impulse to turn to the text springs from the same place that led him to EST. His optimism and self-reliance and bounding trust in personal transformation are, as we’ll discover, very American. So is his belief that he can get away clean.