With untold millions at risk after the Chernobyl explosion, nuclear physicist Ulana Khomyuk makes a desperate attempt to reach Valery Legasov, a leading Soviet nuclear physicist, and warn him about the threat of second explosion that could devastate the continent.

Lyudmilla Ignatenko, a Pripyat resident, ignores warning about her firefighter husband's contamination. Valery Legasov lays out a decontamination plan, complete with human risks.