Valery and Boris attempt to find solutions to removing the radioactive debris; Ulana attempts to find out the cause of the explosion.

Cast: Jared Harris, Stellan Skarsgård, Jessie Buckley, Robert Emms, Barry Keoghan, Adam Nagaitis, Con O'Neill, Ian Pirie, Adrian Rawlins, Paul Ritter, Sam Troughton, Emily Watson