Many people are convinced that Washingtonians — or at least those who work for the federal government — don’t actually live on the same planet as the rest of the country. Kathleen Ann Goonan’s This Shared Dream” suggests that this view is almost right. This excellent science fiction novel is part “Inception,” part “Back to the Future,” part “Jumanji” — and it takes place almost entirely in Washington and Northern Virginia.

When the novel opens in 1991, Sam Dance, an engineer, and his wife, Bette, a Montessori teacher, have been missing for a long time. First, Bette simply vanished in 1963; then, more than a decade later, Sam did the same. No one knows why they disappeared or whether they are alive. The couple did leave behind a rambling old house, with a perennial trust set up for its maintenance and care. They also left behind three now grown children, Jill, Brian and Megan, who have been more or less scarred by the mysteries surrounding their parents’ lives and their own childhoods.

Rumor has it, for instance, that Bette may have been an elite OSS spy in Europe during the 1930s and ’40s. Sam definitely served in World War II with his friend Wink, and the two seem to have been involved with research into a force more powerful than atomic fission. A device harnessing this mysterious energy has even been envisioned by the enigmatic Eliani Hadntz, a brilliant physicist (and physician) who believes that the world could be made more humane through the right kind of early childhood imprinting and the reinforcement of empathy in people’s brain chemistries.

In the first chapter of “This Shared Dream,” the 41-year-old Jill Dance is just finishing her last class as a PhD candidate in political science at Georgetown University. Though generally a superb student, she occasionally makes strange errors, once hurriedly writing in a paper that John F. Kennedy was assassinated in 1963. Which, of course, isn’t true. “Kennedy had not been assassinated,” she recalls, when confronted about it. “Not here. He was an international statesman, a celebrity, the father of the space program, as well as the father of several children born to women not married to him.”

By the novel’s second chapter, Jill has been incarcerated in St. Elizabeths for probable schizophrenia. In reality, she secretly bears a horrible burden: Twenty years earlier she destroyed an entire world, and possibly her parents as well.

‘This Shared Dream’ by Kathleen Ann Goonan. Tor. 367 pp. $25.99. (Tor Books)

“This Shared Dream” is a sequel to Goonan’s “In War Times” (2007), winner of the John W. Campbell Award, and fans of that earlier book will know immediately what’s going on. But the skillful Goonan offers enough hints to bring new readers quickly up to speed. It’s not giving away anything to reveal that a Hadntz Device was developed and that it can morph into multiple shapes, transmit molecular agents that affect the brain’s empathy centers and somehow be used to navigate time streams. Only a very few people are aware of its existence and capabilities, among them Sam and Bette Dance. They also know that, at times, history reaches a kind of temporal crossroads, a highly charged nexus, and Nov. 22, 1963, in Dallas was one.

Unknowingly exposed to Hadntz material since childhood, flower child Jill once, and once only, was able to travel back in time, leaving a violence-racked 1970 to return to 1963 with the aim of preventing Kennedy’s assassination. Far more happens that day in Dallas than the young woman quite realizes, yet the world is nonetheless changed: In this new time stream, her brother, Brian, won’t be killed in Vietnam, the Middle East won’t erupt in bloodshed, and the distinguished senior statesman Martin Luther King Jr. will be in line to become head of the United Nations. Moreover, computers will develop more quickly, and each person will soon rely on his or her own Q, a sophisticated combination of laptop and communicator — and perhaps something more.

All this would seem much to the good, except that Jill can never let on that the world was once different or that part of her misses that world profoundly, even as she must live with the guilt that her actions in Dallas caused her parents somehow to be eradicated from history or lost in time. Or so she thinks.

At this point, “This Shared Dream” is just getting started, as it shifts smoothly among the viewpoints of Jill; the jazz-loving, ­former-alcoholic Brian; and their sister, Megan, an expert on memory. It soon becomes clear, though, that certain individuals, perhaps within our own government, have learned about the existence and capacities of the Hadntz Device. Some secret, moreover, lies hidden somewhere in the old Dance residence, Halcyon House, perhaps in its library or jazz record collection, perhaps among the childhood games in the attic. The unknown enemies also realize that history has been changed once and, with the power of the Device, could be changed again, perhaps directed down a path to a triumphantly revived Third Reich. To thwart a nexus-changing threat to the world and to those she loves, a desperate time-hopping Bette reemerges in the new 1991. Once there, she dares not reveal herself until she nullifies the dangers swirling around her children. But where is Sam?

Readers of science fiction will recognize some of the elements upon which Goonan draws, in particular the long tradition of time-travel stories and alternate histories, not to overlook those popular novels about secret adepts who manipulate history and run the world. But Goonan doesn’t crank out adventure pulp. While she keeps the reader guessing about all sorts of riddles, she is just as interested in depicting family happiness, the romance of the past, the lingering influence of our childhoods. As a result, she writes beautifully about comic books, board games, make-believe in the backyard, drawing pictures with colored pencils, playing musical instruments, family picnics. At the same time, however, in this novel none of these familiar activities are wholly innocent. For instance, those toy astronauts called Spacies seem to have appeared quite suddenly on the market and spread all around the world, while the young Jill’s comic-book heroine Gypsy Myra clearly resembles Eliani Hadntz.

Washington readers will get an extra kick out of Goonan’s familiarity with our fair city (where she grew up). Major characters attend Dunbar High School, the Dances go to the movies at the Uptown Theater, people ride the right Metro lines, and Jill operates Serendipity Books (in the novel moved from Fairfax to near Key Bridge).

While “This Shared Dream” is plenty exciting and expertly paced, there’s a quietness, a gentleness, throughout. Its characters talk far more than they act. They aren’t just action figures; they’re real people, damaged yet striving, and we come to care deeply about them. Such is the power of art — the real, not imaginary, empathy-creating device. Living up to its title, “This Shared Dream” is ultimately a novel about connectedness, in every sense, and the possibility of greater harmony in what used to be called the family of man. Little wonder that Goonan’s overarching metaphor for earthly felicity is improvisational jazz, the true music of the spheres.

Dirda reviews books for The Post every Thursday. Join his discussion at