This is essentially how the miniseries proceeds: Scientists grow extremely alarmed at the fact that there’s an open uranium core gushing trillions of particles into the air every hour; government officials respond that such a crisis is inconceivable and they should just put the fire out already. (“The official position of the state,” a character says at one point, “is that global nuclear catastrophe is not possible in the Soviet Union.”) Harris’s Legasov, a nuclear physicist, is called in to help, although almost everything he says is ignored. The action veers between ludicrous, Death of Stalin–style farce (the radiation level is reported as 3.6 roentgens per second, since that’s as high as the counters go) and grindingly tense body horror (babies burned bright red, incessant retching, open sores). Johan Renck, who directed all five episodes, instills a sense of visceral fear that culminates in one striking scene where nearby townsfolk bask joyfully with their children under falling flakes of deadly nuclear ash.

For Legasov, Watson’s Khomyuk, and Boris Shcherbina—a party official charged with overseeing the crisis, played by Stellan Skarsgård—the challenge is two-pronged: They have to somehow contain a leak that could kill millions of people, and contaminate farmland and drinking water for centuries, while wrestling with officials who deny the evidence offered by their own eyes. (“You didn’t see graphite on the ground,” Dyatlov rants in one scene, shortly before vomiting and passing out. “You didn’t. Because it’s not there.”) Khomyuk has a kind of whisper network of fellow female scientists who convey coded information over bugged phones using the periodic table. Shcherbina growls, furrows his brow, and calls Moscow. Legasov delivers speeches that convey surprisingly thorough and digestible information on how nuclear reactors work while also putting the Chernobyl disaster in context. The fire they’re looking at, he explains in one scene, “is giving off nearly twice the radiation of the bomb in Hiroshima, and that’s every single hour.”

All three actors are titans, and they manage to carry off dialogue that could be cumbersome in lesser hands. Skarsgård and Harris both exude weariness like perspiration, with Harris’s features stretched permanently into a grimace and Skarsgård so craggy, he seems carved out of granite. In one scene, Shcherbina delivers a speech about the Soviet history of endurance and sacrifice that’s memorably rousing and nihilistic at the same time. Watson has the quieter, subtler role, but there’s rarely a scene in which her presence doesn’t command attention. She plays Khomyuk with a gentle, semi-Slavic intonation that serves the character and tends to be less distracting than the aggressively English accents of almost everyone else. While not much wears faster than bad Vladivostok burrs from RADA-trained artists, the cadences here are so extremely British that cultural dissonance sometimes sets in.