The Kremlin has a long history of alleged poisoning of its opponents. When Alexey Navalny, the head of the Russian opposition, fell mysteriously ill on an airplane, Clarissa Ward wondered if President Vladimir Putin could be behind it, but proving exactly who committed a poisoning can be tricky. Follow her through an investigation that leads to the front door of a Russian agent and hear what Navalny’s poisoning has meant for the future of the opposition. 

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