An investigation into the incident in August 2020 when Russia's opposition leader Alexei Navalny was taken ill during a flight to Moscow, having been poisoned. While world leaders struggled to get Navalny the treatment he needed, investigative journalists began to piece together what had happened, finding that not only was Navalny poisoned by a Russian security service hit squad, but that they had been following him for several years while developing new variants of the banned chemical weapon Novichok - previously used in the attack in Salisbury.