Millions of people have been watching a film in the past two days that was released by Alexei Navalny, Russia's leading opposition figure, even as he languished in a Moscow jail. The film, presented by Navalny, accuses the Russian president, Vladimir Putin, of embezzlement on the grandest of scales. Mr. Putin is said to be furious. Last year there was an attempt on Mr. Navalny’s life using the nerve agent, novichok. Fingers were pointed at the Kremlin, which has denied any involvement. Navalny went to Germany for hospital treatment and convalescence. He returned to Russia on Sunday and was arrested on arrival in Moscow. Navalny seems likely to find himself behind bars for several years, but he’s called on his supporters to take to the streets. The Kremlin’s reaction to his return indicates its nervousness. There are parliamentary elections later this year. So what has Vladimir Putin to fear from Alexei Navalny?

Producers: Tim Mansel, Sally Abrahams, Kirsteen Knight