Who was behind this act of sabotage? Was it ordered by Russian President Vladimir Putin, or did the US government have something to do with it? Can the people who carried it out be traced to Ukraine? For months, a large team of journalists worked to track down the alleged culprits. They spoke with investigators and researchers while looking into a variety of theories and motives - to find answers to one of the most secret acts of sabotage of our time. The joint research conducted by the ARD-Hauptstadtstudio, political TV program "Kontraste”, public broadcaster SWR and newspaper "DIE ZEIT” - along with international partners - sheds light on how the attacks were prepared.