When the agents suspected of poisoning Sergei and Yulia Skripal with Novichok left Salisbury, what did they do with the nerve agent and how did the deadly chemical weapon end up in the hands of Charlie Rowley four months later? In this episode, we hear the most likely theories from Counter Terror Police and discover why some parts of this mystery are still unsolved. The Russian state and the suspects have always denied any involvement.

This episode was made by Marie Lennon, Andy Howard, Tom Ryan & Dan O’Brien.

Executive production by Mary Sanders and Naomi Wordley.