Photo: New York Times

At the heart of Caliphate, the New York Times’ limited audio series on the Islamic State, is an ineffable horror. Such is the nature of terrorism: Beyond extreme violence, terrorism typically expresses itself by conjuring a shadow of fear that looms over millions of people. The shadow is intentionally amorphous, a strategic gambit premised upon the idea that the only thing more horrifying than the threat you know is the threat you don’t — not the monster that stands before you, but the one in the dark whose capacity for hurt is as an endless as your imagination. The fear is a thing that metastasizes, narrowing lives and forcing bad decisions. When wielded with purpose and persistence, that fear inspires enemies to defeat themselves.

In a sense, the Islamic State is a kind of ghost, one expands its influence through the economy of ghost stories. The theoretical goal of an podcast like Caliphate, then, is to challenge those narratives by making the unknown slightly more known, the ineffable slightly more effable. In that pursuit, Caliphate, which concluded its ten-episode run on Saturday, is doing something virtuous — even as it reveals a reality far worse than what we ever could have imagined.

The podcast is led by two voices: Rukmini Callimachi, the Times’ foreign correspondent and resident terrorism expert, and series producer Andy Mills, who plays Watson to Callimachi’s Holmes. Caliphate is a kind of spinoff from The Daily, the Times’ groundbreaking daily news podcast, and it inherits many genes from its parent program. The limited series is eminently thoughtful and gorgeously produced, with much credit due to the close attention paid to sound design and the intelligent deployment of scoring. All of it contributes to the feeling of being guided from beat to beat by a hand that’s focused, but not overbearing. It is, for lack for better term, emotionally responsible; the show is very good at creating a space that treats the material with sufficient gravity and dignity, never once tipping into obvious performativity. And when it grapples with the horrors of its subject matter — knife piercing into flesh, a war-torn scene speckled with bodies, the enslavement of minors — the production is very good at letting the scenes, or the stories, vividly speak for themselves.

The most interesting, and perhaps challenging, thing about Caliphate is its structure. The series plays out across ten chapters, but it’s principally organized around a triptych of setpieces: an extensive interview with a former ISIS recruit, a dash into liberated Mosul, and a gripping look at the Islamic State’s sexual enslavement of young Yazidi girls. The podcast’s choice to layer the three narratives on top of each other is an intriguing one. Functionally, it allows the team to better deliver a sense of the collective by shifting between different components of the beast within one narrative thread, from the psychology that motivates ISIS’s growing ranks, to the bureaucratic and operational architecture of the group, to the depths of the suffering and stakes of the conflict.

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Callimachi, Mills, and their team cover quite a bit of ground this way, but the way they transition between the three setpieces, and the relationship of those setpieces to each other, doesn’t necessarily gel with ease. The first half of the podcast focuses on the former ISIS recruit, a young Canadian man who comes from what one might describe as a seemingly normal background, with the key mystery being the specific things that drove him to join the Islamic State. That story forms the backbone of the whole series, and at the risk of spoiling the narrative, I’ll just say that the story contains an unexpected turn, one that shifts the setpiece from a slow-burn psychological examination to a thrilling chase after a truth that may or may not be found. Caliphate absolutely flourishes on this turn, skirting the lines of a traditional documentary and something that threatens to bursts through your headphones gasping for air. For a moment, the thing you’re listening to feels very much alive.

And then, almost as quickly as the story twists, the narrative switches focus to the next setpiece. It doesn’t quite abandon the tale of the former ISIS recruit throughout the following scenes — we hear a reference to him as the series follows Callimachi and Mills through a bombed-out Mosul — but the switch-up evokes a little whiplash. The thread dangles, unnervingly, for a long time. Chekhov’s gun is a mechanism that can easily be deployed in fiction, but in the realm of nonfiction and documentary, you must grapple with the fact that a thread left unresolved can be left hanging forever. The knowledge of that thought has a way of looming, distractingly and hauntingly, over whatever story you’re following next.

The choice to build a narrative around multiple setpieces without immediately clear relationships is due, in large part, to the nature of the production. “A lot of the early meetings were like, ‘We have a lot of stories that we can tell.’ There are just so many layers of complexity,” Larissa Anderson, the podcast’s managing producer, told Vulture in April. “We needed to pick one ambitious thing and really lean into it.” In this case, they picked three ambitious things, and the team sought to package it all together in one bundle that illuminates the essential question at hand: “Who are we fighting, anyway?”

The result is a project that grapples with a core tension within documentary and nonfiction: How does one squeeze the messy complexities of the real world into a clean narrative? That tension is exacerbated by the very nature of the subject matter — again, it’s literal terrorism — which wields narrative incorporeality as a key weapon in its pursuits. How does one squeeze the messy complexities of something as horrifying and sprawling as the Islamic State into a narrative that you can easily grasp? That is, into something effable?

Caliphate ultimately returns to the story of the ISIS recruit in its final chapter, as a way to come full circle and close out the series. Again, at risk at spoiling the end, I’ll just say that the thread doesn’t actually end up getting resolved. Then again, how can it? Wouldn’t a clean resolution be antithetical to the pursuits of a project that seeks to illuminate the nature of terrorism? Those questions are perhaps among Caliphate’s biggest contributions: It reinforces the idea that there are no real endings in documentary or journalism, and that the way to truly cut into an unknown is to reckon with its unknowability.