Dr Ruja promised financial revolution. And then, two years ago, she disappeared. Why?

The Missing Cryptoqueen is an eight-part series for BBC Sounds, with new episodes every Thursday.

Presenter: Jamie Bartlett
Producer: Georgia Catt
Story consultant: Chris Berube
Editor: Philip Sellars
Original music and sound design: Phil Channell
Original music and vocals: Dessislava Stefanova and the London Bulgarian Choir