Dr. Ruja Ignatova, mastermind of the OneCoin cryptocurrency scam, vanished in 2017 after defrauding investors of over $4 billion. A BBC investigation reveals her ties to Bulgarian crime boss Hristoforos Amanatidis, known as Taki. Allegations suggest Ignatova was murdered on Taki's orders in 2018, though her body remains unfound, leaving her fate shrouded in mystery.