Please Remain Calm

S1, E2: Seven hours after the Chernobyl explosion, Ulana Khomyuk, a nuclear physicist in Minsk, is awakened in her office by a radiation alarm and grows increasingly worried when her phone call to Chernobyl goes unanswered. Lyudmilla arrives at the Pripyat hospital looking for Vasily, whom she learns is being helicoptered to Moscow. At a Central Committee meeting with General Secretary Gorbachev, Legasov objects to Deputy Prime Minister Boris Shcherbina's assessment that the situation is contained, and Gorbachev ends up sending both men to Chernobyl, where a new reading shows radiation is thousands of times higher than reported. Legasov urges Shcherbina to evacuate Pripyat, but Shcherbina worries about Moscow's reaction. As reports of the disaster spread to Europe, Shcherbina finally calls for an evacuation, even as Khomyuk makes her way to Chernobyl to warn Legasov and Shcherbina that a second and far more massive explosion is imminent – one that puts the entire European continent at risk.