When we meet in Moscow, the editor-in-chief of Novaya Gazeta and Russia's Nobel Peace Prize laureate is worried how far the Kremlin will go in its confrontation with the West.
"Two generations have lived without the threat of nuclear war," Mr Muratov tells me. "But this period is over. Will Putin press the nuclear button, or won't he? Who knows? No one knows this. There isn't a single person who can say for sure."
Since Russia launched its full-scale invasion of Ukraine in February 2022, Moscow's nuclear sabre-rattling has been loud and frequent.
Senior officials have dropped unsubtle hints that Western nations arming Ukraine should not push Russia too far. A few days ago, Russian President Vladimir Putin announced plans to station tactical nuclear weapons in Belarus.
Then one of his closest aides, Nikolai Patrushev, warned that Russia had a "modern unique weapon capable of destroying any enemy, including the United States".
Bluff and bluster? Or a threat that needs to be taken seriously? Mr Muratov has picked up worrying signs inside Russia.