The Russian activist Aleksei Navalny has spent years agitating against corruption, and against President Vladimir Putin. Last summer he was poisoned with a rare nerve agent linked to the Russian state. Last week, after recovering in Germany, he returned to Moscow. He was arrested at the airport, but he managed to put out a call for protest, which was answered in the streets of more than a hundred Russian cities. Today, we look at the improbable story of Aleksei Navalny.