As Fail Safe proceeds and the military-nuclear apparatus kicks into full gear, the men tasked with operating within it try to find ways to hang on to what humanity they have left—and so, in Lumet’s hands, it becomes a film of faces, at times immense, downright expressionistic ones. Consider the sequences in the White House bunker with the president and Buck on the phone with the Soviet premier. When the president first makes the call, he and Buck are each confined to their individual frames, with the phone looming large in the foreground, a simple object given monumental power. Then, in what may be the film’s tensest scene, we see the two men sit in a more straightforward two-shot, each on opposite sides of the table, the phone now normal-sized at the center of the frame. The camera remains fixed, and Lumet doesn’t cut away as the president speaks to the Soviet leader; Buck not only translates but, at the president’s urging, tries to gauge the Russian’s emotional state. It’s an attempt to navigate the technology and find traces of the very real person on the other side of the line.

Later, as the president speaks to the premier and to the two nations’ ambassadors in New York and Moscow, informing them of his plans to bomb New York after Moscow is destroyed (thus also softly informing the two ambassadors that they will be killed in the respective blasts), we see Fonda in close-up, this time with his face obstructed by his hand against his forehead. Again, Lumet holds on the shot, so that this pivotal, agonizing scene plays out without our being able to properly glimpse the actor’s visage. We can certainly understand the president’s anguish, but we don’t really see it—nor, interestingly, do we really feel it. This is Fonda in his classic rational-humanist mode, and yet there’s something horrific about his demeanor too. It is as if the system has incorporated him. He is proposing the one solution that will prevent a worldwide atomic exchange—a limited nuclear self-sacrifice that will result in a “mere” few million civilians dead—but we will soon learn that in doing so he is condemning his own wife to death as well. So the fact that he has to play it as a sober, levelheaded decision feels like its own harrowing defeat.

And then there’s the final time Lumet presents Buck and the president on-screen. It’s the last conversation they have with the premier, who has informed the Americans that his forces will stand down, and that he takes the president at his word. Lumet starts this scene in fragmented, alienating profile shots of Buck and the president, each covered in dark shadows. Buck translates the premier’s words, but the scene is filmed as if he and the president were having a conversation with each other, almost as if Buck has been possessed by the premier. “This was nobody’s fault,” Buck says. “No human being did wrong.” “I don’t agree,” the president responds. “We’re to blame, both of us. We let our machines get out of hand.” As he speaks, the camera starts to move ever so slightly, and his face begins to emerge from the shadows—so that by the time the president says, “What do we do, Mr. Chairman? What do we say to the dead?” we see Fonda in full close-up, his eyes staring directly into ours. Buck’s face comes into the light, too, so that both of them are now looking right at the camera, and at us: “I think, if we are men,” Buck translates, “we must say this will not happen again.” It’s not a subtle effect, to be sure, but by foregrounding the actors’ faces, in all their sweat and tension and heartbreak, Lumet avoids any potential for didacticism, turning this into a moment of overwhelming communal sadness.

In some ways, Lumet’s clear-eyed melancholy in Fail Safe serves a function similar to Kubrick’s delirious buffoonery in Strangelove—it shocks us into paying attention to the absurd moral calculus of this situation. These extremes also allow both movies to transcend their respective source material. The echoes between the two works may not have been entirely coincidental. Kubrick and Peter George, the author of Red Alert, the (dead-serious) novel upon which Dr. Strangelove was based, even sued Burdick and Wheeler—along with the film’s production company and others—for copyright infringement. The suit was settled out of court, but, according to Lumet, one condition was that Kubrick’s distributor, Columbia, would also buy the independently produced Fail Safe. Lumet’s picture had gone into production ahead of Dr. Strangelove, but Columbia released Kubrick’s film first. In the wake of that movie’s zeitgeist-defining success, the earnest drama of Fail Safe must have seemed like a sad transmission from the past, and it quickly faded from the box office.

So why has Fail Safe endured over the years, despite this initial disappointment? Lumet’s ensuing career certainly helped, as he would go on to helm some of the most important American pictures of the sixties and seventies. The power of its subject matter surely contributed as well—and is probably one of the reasons the film resonates so specifically today, when nuclear fears, once supposedly vanquished by the end of the Cold War, have come charging back. But ironically, Dr. Strangelove probably helped too. As Kubrick’s comedy went from box-office hit to epochal classic, it brought Fail Safe along with it, like a cinematic phantom limb, a direct expression of the human sense of tragedy that is Dr. Strangelove’s defining absence.

“I’m not directing the moral message,” Lumet said of his body of work in a 2008 interview, featured in the documentary By Sidney Lumet. “I’m directing that piece and those people. And if I do it well, the moral message will come through.” It’s a rewarding way to look at the dilemmas featured in his pictures, many of which show individuals—whistle-blowers and turncoats, crooks and cops, politicians and ordinary people—coming into conflict and undermining systems designed to chew them up. But in Fail Safe, he shows us a system built on the very denial of humanity, one in which individual efforts are completely ineffective and bravery is rendered useless. This is the one Lumet film that presents us with a world in which morality is impossible. And it is the world we have been living in for decades, and continue to live in today.