On March 4, 2018, emergency services descend on Salisbury city centre where they find former spy Sergei Skripal and his daughter Yulia unconscious on a park bench. They are taken to hospital where doctors struggle to diagnose the source of their illness, while DS Nick Bailey decides to investigate the Skripals' home for further casualties, but soon after returning to work he too begins to feel ill. Fact-based drama, starring Rafe Spall and Anne-Marie Duff.