The Skripals and DS Bailey fight to survive, whilst the Director of Public Health in Wiltshire, Tracy Daszkiewicz, and the emergency services try to locate the source of the nerve agent to prevent further casualties.
CID officer Nick Bailey's condition worsens as Tracy struggles to protect local residents against the numerous deposits of Novichok being found across the city.
The decontamination efforts finally show results and eventually life in Salisbury returns to normal. However, a mistake with good intentions creates a resurgence of the poison, causing Tracy’s life to spiral just as she was beginning to fix it.
Nick struggles to adjust to life post-Novichok; Tracy learns that the contamination radius may be even bigger than last time; and the poisoning proves fatal for Dawn Sturgess.
Anne-Marie Duff
Tracy Daszkiewicz
Rafe Spall
DS Nick Bailey
MyAnna Buring
Dawn Sturgess
Mark Addy
Ross Cassidy
Annabel Scholey
Sarah Bailey