While travelling to work on Waterloo Bridge in 1978, Markov, a Bulgarian dissident working for the BBC, collided with a man carrying an umbrella. Markov felt as if he had been stung by something, but thought no more about it. Three days later he died. What had looked like a curious accident became one of the most notorious stories of the Cold War.
Thirty years on it remains unsolved, but the film discovers shocking new information revealing that Scotland Yard interrogated the prime suspect in the case in 1993, and released him shortly afterwards.
The trail leads journalist Jack Hamilton to Copenhagen, where he discovers some surprising information about the man at the centre of the Georgi Markov murder.