April 26, 1986, Ukrainian SSR. Plant workers and firefighters put their lives on the line to control a catastrophic 1986 explosion at a Soviet nuclear power plant.

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.

Valery Legasov, Boris Shcherbina and Ulana Khomyuk risk their lives and reputations to expose the truth about Chernobyl.