number of people in litvinenko 's past who may have wanted him dead. the fsb colleagues he denounced. the russian mobsters he was investigating. perhaps someone who thought he was a traitor for working with british intelligence. for years now, litvinenko widow, marina, has been asking how big was a conspiracy? who was behind it? how high did it go? dangerous questions that she knows better than anyone? >> you think you play chess, but they play russian roulette. >> those who were closest to litvinenko believe the kill order may have come from the very top. because litvinenko picked a fight with the wrong person from his past. none other than russian president, vladimir putin. >> sasha was on a mission. he was trying to prove that is that putin is as corrupt as anybody. >> the mission may have started