There are moments in a good play when you can feel the temperature of the room drop several degrees. This happens several times in “Giant,” a crackling, substantive new drama by Mark Rosenblatt now on Broadway, but the first instance sets the tone. The legendary children’s author Roald Dahl (John Lithgow) is being visited at his English country home by two concerned representatives from his publisher: a British managing director, Tom (Elliot Levey), and an American sales director, Jessie (Aya Cash). Amid lemonade and light banter, Jessie has asked Dahl to sign one of his books for her son—when out from its pages tumbles a folded photocopy of an article, heavily annotated.

“My scandalous book review!” Dahl exclaims. Indeed: This is the infamous 1983 article in which Dahl, reviewing a book detailing the casualties of Israel’s siege of Lebanon the previous year, went beyond considered criticism of Israel’s military to excoriate Jews in general as “a race of people” who had “switched so rapidly from being much-pitied victims to barbarous murderers.” Jessie’s scribbles in the margins alert Dahl to the battle lines he’s about to engage on: His publisher would like him to make a public statement disavowing antisemitism, lest the controversy over his offending comments dampen sales of his forthcoming book The Witches.

The chill that descends over the conversation is unmistakable, and it never quite lifts from this taut play of ideas, which has the outward appearance of a drawing room comedy but the tension of a thriller. That is partly due to the startling timeliness of its debate, as we are living through yet another period in which criticism of Israel and its influence over U.S. foreign policy is intersecting, in complicated ways, with a terrifying rise in open antisemitism.

It also has a lot to do with the performance that towers, literally, over Rosenblatt’s play: Lithgow as Dahl is one of the most inspired matches of actor and role I can recall. Looking a bit like a Gerald Scarfe caricature come to life, Lithgow can flash with mercurial precision from a scowl to a twinkle, and from verbal combat to piercing compassion, and his voice can modulate from thundering timpani to delicate piccolo (these are among the assets that made him a memorable King Lear for Shakespeare in the Park in 2014). He’s a natural, in short, for the role of Dahl, an author known for his unique blend of humor and horror, empathy and cruelty, whose ornery, unbiddable personality shone through every page, from Matilda to BFG to Charlie and the Chocolate Factory.

Dahl, at least as Rosenblatt imagines him, also happens to be an ideal theatrical subject. He’s witty and mischievous, for starters, but more importantly, he is the kind of provocateur who always seems to be spoiling for an argument—who never met a silence or subtext he didn’t want to pry open. In the midst of an impasse with Jessie, who has tangled hotly with him over Israel and antisemitism, Dahl turns to his sunny young chef, Hallie (Stella Everett), and bluntly asks, “What do you think, darling girl?… Would you buy an Israeli avocado?”

And Dahl can’t resist turning viciously on one of his allies in the fight, calling his publishing representative, Tom—a secular Jewish Brit whose strongest feeling about his identity is exasperation that he’s expected to have an opinion on Israel—“a house Jew.” Alongside Tom, Dahl’s stalwart, chipper fiancé, Liccy (Rachael Stirling), tries in vain to put out the fires he starts. Under director Nicholas Hytner, all the actors hold their own admirably against Lithgow’s formidable center of gravity, although Cash, a talented comic actress, is shouldered here with the thankless task of playing aggrieved righteous anger throughout.

Rosenblatt’s subject is not only antisemitism per se but the ever-relevant dilemma of separating the art from the artist. Can we enjoy the work of writers and artists about whom we’ve learned terrible things? Well, “MJ the Musical,” a celebration of Michael Jackson’s music that studiously sidesteps allegations that he sexually abused children, is playing to capacity audiences a few blocks from “Giant,” while a new production of Wagner’s “Tristan und Isolde,” a bit further uptown at the Metropolitan Opera, is currently drawing raves, with its composer’s noxious antisemitism barely a footnote.

Similarly, Dahl’s work seems in no danger of cancellation. When Dahl asks Jessie how she can keep reading his work given what she knows about his views, she concedes, “I don’t know if everything you are, the books are too.” And Rosenblatt gives Tom a stirring encomium to Dahl’s singular genius:

In his books, he…picks a glorious, playful path through the chaos of childhood. It’s the rarest of gifts. To show its cruelty but take you out the other side. And the more kids feel guided by his books, the more boldly they’ll read as adults, travelling way beyond the narrow crap their parents told them to sit with braver minds in ever richer worlds.

They will need those “braver minds,” since the “ever richer worlds” Tom idealizes in that lovely statement also bring with them thorny, uncomfortable questions. In the world outside of novels, let alone even the best children’s books, we are faced with nonfictional issues of war, genocide, authoritarianism, hate crime. The tragedy of Dahl’s antisemitism isn’t that it colored his art but that it clouded his vision and tainted his outrage. It’s a lesson we would do well to take to heart today, as the U.S. embroils itself in a war with Iran at least partly on Israel’s behalf. To see clearly what is before us, amid both the fog of war and the specter of entrenched prejudices, is a moral imperative. And, as “Giant” incisively shows, lowering the temperature of our passions is one way to stay clear-eyed and frosty.

Rob Weinert-Kendt, an arts journalist and editor of American Theatre magazine, has written for The New York Times and Time Out New York.