A few months ago, the Canadian novelist David Bezmozgis wrote an essay about Russia’s annexation of the Crimean Peninsula. Like most observers, he was distressed by the violence in the region and the prospects of military escalation. Yet he also had a somewhat more selfish concern: For four years he had been working on a novel about an Israeli politician who flees to the Crimean city of Yalta after a personal scandal hits the front pages. “I’d wanted to write a novel that, among other things, engaged with current politics,” he wrote; instead, “world events conspired to undermine my designs for the book.”

Mr. Bezmozgis surely had a few dark nights of the soul. Yet “The Betrayers” seems only to benefit from its sudden disconnection from the headlines. Set in a parallel reality in which Israel has voted to withdraw from its West Bank settlements and Crimea is still an uncontested part of Ukraine, the novel takes on contentious questions about Zionism and the fate of post-Soviet Jewry, undistracted by the caprices of the news ticker or the polemics of the moment. It bears out Israeli writer Amos Oz’s claim that “the novelist has no political aim but is concerned with truth, not facts.”

At the heart of “The Betrayers” is the magnetic Baruch Kotler. He is a former refusenik—a Soviet Jew denied permission to emigrate to Israel—who was imprisoned in Russia for 13 years after a show trial found him guilty of treason. Finally released, he arrived in Israel a “dissident champion” and formed a staunchly right-wing Russian immigrant party, which he has led with outspoken pugnacity for more than two decades. He is “famously stubborn” in a “notoriously obstinate country,” and Mr. Bezmozgis brilliantly captures a man who is as flawed as he is principled.

This description will quickly call to mind the former Israeli politician Natan Sharansky, but Kotler has been extensively fictionalized. In particular, Mr. Bezmozgis implicates him in an affair with a headstrong young staffer named Leora (no such scandal has ever been attached to Mr. Sharansky). When Kotler speaks out against the Israeli Parliament’s plan for unilateral withdrawal, his opponents leak incriminating photos. “The scandale Kotler” becomes 24-hour-a-day news, and he sneaks out of the country with Leora, flying to Yalta.

The action of “The Betrayers” takes place during the two days of that trip. For Kotler, Yalta is more than just a spot to hide out. It was the resort where he, like so many “rank-and-file Soviet citizens,” summered as a child. Thus his great lapse sets in motion a reckoning with the land and people he believed he had put behind him—a reckoning that is instigated when he and Leora rent a room from a local pensioner and discover that her husband is none other than the man who denounced Kotler to the KGB.

“The odds of this, of ending up a boarder in his house, are almost nil,” Leora observes. But in the condensed, fable-like atmosphere of “The Betrayers,” the coincidence has a feel of inevitability, as it pits two strong-willed, compromised but unrepentant adversaries in a kind of ethical standoff. The novel largely stays in Kotler’s point of view but intersperses chapters that comprise a surprisingly compassionate depiction of his nemesis, Chaim Tankilevich. He lives in impoverished, semi-anonymous disgrace, surviving on a subsidy from the local Jewish charity. (The charity’s organizer knows of Tankilevich’s past as a KGB informant and exacts onerous terms for the small monthly sum.) Tankilevich believes that he collaborated only under duress and that his decades of hardship have been punishment enough—and furthermore that Kotler, who enjoys fame and prestige in part because of the betrayal, should publicly absolve him.

The two men’s confrontation becomes a dialogue about moral authority. Mr. Bezmozgis presents it with sympathy and perceptiveness, taking us deep into the thoughts of both Kotler and Tankilevich. Considering his right to act as a spokesman for the Jewish people, even when doing so puts him in the political cross hairs, Kotler thinks: “One sacrificed for one’s people as one sacrificed for one’s children. One did it because one felt that one knew better than they did. That one saw in them what they failed to see in themselves. One kept faith as God kept faith with the Israelites, the stubborn stiff-necked people, complaining even at the moment of their redemption, turning their backs, endlessly squabbling, quick to forget signs and wonders.”

But the man who acts as a stand-in for God is also committing an act of hubris. “So you were born a saint and my husband a villain?” Tankilevich’s wife rhetorically asks, suggesting that Kotler’s inflexible principles, combined with his betrayal of his wife, make him guilty of vainglory and hypocrisy. Further revelations show that Tankilevich is also a man of passionate loyalties, but they are for his family rather than the whole of the Jewish people.

Slyly and provocatively, the drama doubles as an inquiry into modern-day Zionism. Kotler is a hard-liner because his belief in the Israeli homeland grew from personal resistance to tyranny; his very identity is bound up in Zionism’s struggle, even if it seems never-ending. “What dreams they had nurtured and what distortions now obtained,” he thinks of his fellow dissidents. “And it was all to do with land. . . . Was there a more primitive concept? But nobody lives in the ether. Man is a physical being who requires physical space. And his nature is a prejudicial nature of alike and unalike. That was the history of the world.”

Readers will no doubt have vehement and divided reactions to Kotler’s politics and beliefs. But the point of this novel is not to affirm or undermine any particular position. Mr. Bezmozgis accomplishes the higher task of understanding and humanizing his character’s creeds. A reminder that good fiction aspires not to be timely but timeless, “The Betrayers” illuminates old, stubborn arguments that usually inspire only heat and noise.

Mr. Sacks writes the fiction chronicle in the Weekend Journal.