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It’s a vague, twilit hereafter, this place where Michael Frayn’s three restlessly inquisitive characters circle and challenge and comfort one another—an echoing blue-white void in which time seems meaningless and space folds in upon itself. But what transpires here—what happens in the heady precincts of Copenhagen, in the past of Frayn’s imagination and the half-life of the collisions and decisions he depicts—has everything to do with what one of his characters calls “this most precious meanwhile” we inhabit.

What is it, then, that happens in Copenhagen? Any number of things, and nothing certain. Frayn’s inspiration is the famously mysterious visit paid by German atomic scientist Werner Heisenberg to his mentor, the Danish physicist Niels Bohr, in 1941—when the latter’s country had been occupied by the former’s, and their opposing governments were racing to build an atomic weapon. Did Heisenberg come to Copenhagen to fish for information about the Manhattan Project? To warn Bohr of a Nazi equivalent? To sound him out on ways of speeding or subverting the bomb-building efforts? Or simply to ponder the ethics and politics involved? No one quite knows what transpired, the best efforts of historians notwithstanding, so Frayn uses the incident as the jumping-off point for a meditation on the moral and philosophical implications of a science that’s come adrift from its humanist moorings—and for a tender, heartfelt consideration of the human impulses that sometimes strain the anchor ropes. In Copenhagen, from the vantage of an afterlife reunion, the two men and Margrethe Bohr relive and re-examine the visit over and over again, looking for motivations and meanings, trying to understand how decent people (and don’t most of us think of ourselves that way?) could create a world in which horrors like the bomb seem not merely possible but necessary. The result is a play that explodes with ideas, with energy, and with feeling.

Or with ideas, anyway, in Jim Petosa’s production for the Olney Theatre Center, which comes barely two years after the Kennedy Center hosted the touring incarnation of the Tony-winning Broadway production. The energy flags occasionally, though, and the feeling sometimes seems a trifle muted.

Physically, this new version is a marvelous staging: James Kronzer’s clean, coffered box of a set might be a bunker or a laboratory or a mausoleum, and Daniel MacLean Wagner does seductive, suggestive things with the lights (chill and watery and warm by turns) that flicker and wash over it. A near-subliminal pulse of sound reverberates occasionally, its unsettling double thump a reminder from designer Tony Angelini of the stakes in this conversation. A silvery disc dominates the cobalt wall at the back of the stage, except that when you look closer, it’s not a disc at all; it’s only a half-moon completed by its own reflection, a half-truth made whole by a trick of the light and an act of complicity in the mind. That eloquent design gesture, together with the constantly shifting mood of the playing space, underscores and reinforces Frayn’s ideas about the mutability of memory (“a curious sort of diary”) and the final impossibility of self-knowledge. Heisenberg’s uncertainty principle, it turns out, describes more than just subatomic particles.

The trouble isn’t anything to do with Christopher Lane’s Heisenberg, whose surface composure belies a profound emotional turmoil from the very start. (Watch his eyes when he describes his arrival at the train depot, a conspicuous civilian “among all the field-gray Wehrmacht uniforms…all the naval gold braid, all the well-tailored black of the SS.”) Lane’s resolutely contained mien is the stolid mask of an intensely self-conscious man whose occasional flashes of arrogance conceal a deep-rooted doubt about his own abilities; the actor’s sensitive portrait of a deeply conflicted Heisenberg adds richness (and a certain irony) to the play’s already nuanced contemplation of the man, and when the anguish finally erupts from behind that control, it seems a shattering thing.

Nor is there anything particular lacking in Valerie Leonard’s Margrethe. There’s a certain theatricality to her demeanor, yes, a slightly outsize way of watching and reacting to what passes between her husband and his protégé. But then watching and reacting is no small part of what Margrethe is asked to do—when she’s not standing in for the scientifically challenged audience as the men bandy theories. (“In the end, remember, we have to be able to explain it to Margrethe,” Bohr points out when an argument gets especially knotty.) She’s the play’s conscience, Frayn’s constant reminder of human consequences. And she’s its truth squad, too, gently (sometimes brutally) challenging Bohr and Heisenberg when they rationalize or sentimentalize or gloss over something crucial. Leonard makes her a warm, wise figure; you admire her patience and ache for her pain.

Alan Wade’s genial, avuncular Bohr may be part of what seems unbalanced about the Olney production. Wade has the requisite dignity, certainly, but there’s nothing formidable about him, no sense of the terrible, Godlike figure Heisenberg describes in a crucial Act 2 passage. And Wade communicates little about what makes Bohr such a moral authority to his peers; when he contemplates his critical contribution to a technology that eventually destroyed hundreds of thousands of lives, it seems a small shrug of a moment rather than a colossal, tragic thing.

Also troubling is the sense that Petosa hasn’t found the balance between the play’s intimate tragedies and its epic concerns. The genius of Copenhagen is in the exquisitely painful parallels it finds between the specific courses of its three lives and the sweeping trajectories of history and human experience, but the latter seem more urgently at issue here—and so something of the play’s immediacy is lost.

Perhaps most disconcerting on opening night, though—although least worrisome, in that it’s the sort of thing that improves—was the feeling that the ensemble hadn’t quite jelled, that the actors hadn’t entirely gotten their heads around the language and the science and the philosophy of Copenhagen. With that mild awkwardness in the air, Act 1 seemed like a marathon, the bulk of Act 2 a circular, repetitive conversation rather than a spiraling, galvanic one. Only in the last stretches, with Heisenberg facing a moment of awakening and all of them facing the only inevitable end to human uncertainty, did the play gather its energies and threaten to overwhelm.

The five weeks of the Olney run isn’t quite the eternity Frayn’s threesome contemplates in that cool blue void, but it’s more than enough time for Petosa and his company to come fully to grips with the play. In the meanwhile, it’s enough to consider the comforts of uncertainty. As Frayn ever so gently demonstrates in Copenhagen, it’s all that separates us from the void. CP