There is no contemporary practitioner of the art of historical fiction more accomplished, in my view, than Thomas Mallon. His forays into the past have ranged from small-town life in post-World War II America (in Dewey Defeats Truman), to the frantic world of magazine publishing in the 1920s (in Bandbox), to the eponymous couple in Henry and Clara, who accompanied Lincoln and his wife to Ford’s Theater on the night of his assassination. (The latter, I think, is nothing short of a masterpiece.)

In “Writing Historical Fiction,” an illuminating essay reprinted in In Fact, a collection of his nonfiction, Mallon posits that readers in our increasingly ahistorical society “no longer go to historical fiction for explanation so much as for exoticism.” Such a development, he writes, is neither regrettable nor exceptional: “readers always liked historical fiction not because they wanted to drag history into the present and make it useful, but because they wanted to put themselves back into history, into the past, to wander as if in a dream, to ponder themselves as having been born too late-a much more common feeling than the feeling one has been born too soon.”

Mallon has a knack for making the past immediate and real, creating worlds at once utterly engaging yet marked by the “exoticism” that makes them fundamentally different from the present. Fellow Travelers, Mallon’s latest contribution to the genre, is framed by the denouement of the cold war but set mainly against the background of the McCarthy hearings in the early and mid-1950s. In reading it, however, I plead guilty to feeling more like a returnee to the once-familiar landscape of childhood than a tourist in an exotic setting.

My father was a New Deal Democrat from the Bronx who lost his congressional seat in the same Republican electoral sweep of 1946 that made Joe McCarthy junior senator from Wisconsin and Richard Nixon a representative from California. Among my father’s Democratic pals was Bronx judge Al Cohn, father of Roy Cohn, McCarthy’s chief counsel on the Senate Permanent Subcommittee on Investigations and, in the eyes of many, his co-inquisitor. Like Judge Cohn, my father was nonplussed by Roy’s redbaiting, especially since he chalked up getting the boot from his constituents in part to the Republicans’ success in tarring all Democrats as “soft on communism.”

Debates over McCarthy’s tactics (or, as my father called them, “antics”) filled our living room, the discussion growing more raucous as the cocktails flowed. I listened with a child’s mix of befuddlement and fascination as crimson-faced adults slashed at one another, wielding names and phrases like weapons—Truman, MacArthur, the Rosenbergs, Korea, Alger Hiss, Who lost China?—none of which I entirely understood. It all flooded back as I read Fellow Travelers, not just monikers and events, but ordinary and authentic details: the spic-and-span cleanliness of middle-class kitchens in Manhattan’s Stuyvesant Town (we lived in its Bronx twin, Parkchester); the hard slide of a confessional panel being shut by a priest unhappy with what he’d just heard.

Of course, there’s no need to have personal experience of the 1950s in order to be drawn in by Mallon’s narrative skill. On the contrary, his richly layered story provides an utterly convincing account of no-holds-barred maneuverings afoot in Washington at what seemed the beginning of an epic and endless struggle against aggression abroad and subversion at home. Mallon’s characters are each caught in the complex tangle of ambition and self-interest in which private agonies intersect with international crises. “All of them,” he writes at one point, “were dangling from the world tonight, unaligned nations and shaky protectorates, struggling toward independence or falling into unwise alliances.”

The world Mallon recreates has little resemblance to the oft-invoked image of the ’50s as happy days of innocence and light. In his telling, this is a tense, uncertain time, full of conflicted motives and afflicted souls. Harrowed by crises foreign and domestic, Washington is also haunted by the spirits of controversies past. Woodrow Wilson’s widow, “plump and pretty,” appears at a party atop the Washington Hotel. Alice Roosevelt, T.R.’s daughter, is among the guests at Joe McCarthy’s wedding.

Plus ça change: the action in Washington is always partisan, the animus as much personal as political. The game is called “Who has what on whom?” That question runs like a toxic litany through the book. “What, Tim wondered,...did Cohn have on McCarthy?” “Was Cohn in love with Schine, or was Adams in love with money?” “‘I’ve been trying to figure out what McCarthy has on McIntyre and what McIntyre has on Potter.’” “‘The only thing that counts in all of this is what anybody has on McCarthy.’” Round and round it goes. At its center is the embittered, grievance-filled figure of Tom McIntyre, “his face somewhere between mottled and ravaged,” an ex-newsman who seems to have something on everyone.

The hunt underway in the capitol’s highly charged atmosphere isn’t confined to ferreting out Reds and their alleged “pinko” accomplices. “Are you now or have you ever been a member of the Communist Party?” has a parallel query directed at a different type of fellow traveler. “What’s his problem?” asks one character about another. “Pink or lavender?” Scott McLeod’s Miscellaneous M Unit combs the ranks for, supposedly, moral misconduct of any sort. Its real focus is on sexual conduct of a particular type. Mr. Traband, who heads the “sexual deviation investigations,” confidently affirms the official purpose behind the pursuit: “‘One homosexual can pollute an entire government office.’”

At the heart of Fellow Travelers is the lavender problem. On the day of Joe McCarthy’s nuptials, Timothy Laughlin, a summer intern at the Washington Star drafted into helping cover the wedding, pauses in Dupont Circle to transcribe his notes. He is approached by a stranger, “suit jacket slung over...broad shoulders and the faint glistening of sweat in the hollow of neck where he’d loosened his tie.” Suave and good looking, the stranger leaves Timothy flustered yet certain of one thing: “if he lived to be a hundred, he would never be more in love than he was now.”

The stranger turns out to be Hawkins Fuller, who helps Tim Laughlin secure a position on the staff of Senator Charles Potter, a member of McCarthy’s committee. A love affair ensues—a passing interlude for Hawk Fuller, a lifetime passion for Tim. A graduate of St. Paul’s and Harvard, more than able to hold his own amid the lethal gamesmanship of the capital, Hawk is a rising star in the WASP precincts of the State Department. Tim, a recent graduate of Fordham, is from a New York Irish-Catholic family in the process of transition from Hell’s Kitchen to the Long Island suburbs. Hawk’s cold eye appraises him this way: “Clever. Terribly sincere right-winger. No particular drive. A tender disposition.”

Hawk loves Tim in his fashion, but that doesn’t include committing professional suicide by risking a permanent relationship. Career trumps all else for Hawk. If that requires the masquerade of a heterosexual marriage, so be it. At the outset, Tim is a romantic, believing “that he and Hawkins had lifted themselves above the wrecked earth by doing what they did in bed.” But eventually, this hope gives way to “the realization that joining their bodies only chained them to the electrified cage of who had what on whom.” As with all careerists, Hawk is an uncompromising realist and in a manner both practical and brutal, he does what he believes he has to do to make Tim the same.

The problem is more complex for Tim. His intimate tie with Hawk is complicated by his relationship with God. Mallon is true to the context of the times in which Tim’s struggle takes place. There are no prophetic diatribes against the church’s prohibitions against homosexual sex or prescient announcements of the soon-to-be movement for gay liberation. Mallon is too good a historical novelist—and too subtle a storyteller—to fall into the trap of preaching or didacticism. Instead, he deftly lays out the particulars of Tim’s attempts to reconcile his deepest, innate sexual attractions with his soul-seated love of Christ.

Unlike Hawk, Tim decides with quiet bravery against living forever in the closet and is dismissed from the Army reserve for admitting his homosexuality. His subsequent life seems devoid of grand gestures. He lives in obscurity, in Providence, Rhode Island, a Catholic still, casual in his observances but profound in his faith, a fact conveyed to Hawk years after they parted by a mutual friend: “‘He told me that...he’d realized, all of a sudden, while walking down a street some Saturday afternoon, that he’d spent his whole life trying to make God love him—and that didn’t matter in the slightest. All that mattered was that he loved God. He told me that once he knew that he was home free.’”

A wise and beautifully written novel, pitch perfect in its description of high-stakes political intrigue and individual redemption, Fellow Travelers dispels the illusion of a golden age of political bipartisanship and distils the venomousness and vindictiveness that poison the body politic in every era. As well as reinforcing his reputation as a master historical novelist, Fellow Travelers puts Mallon in the company of Graham Greene—that other chronicler of broken, belief-haunted men and women, heterosexual and homosexual alike, sinners every one, who struggle toward the certainty that the love of God makes all the difference.