In March 2018, former Russian spy Sergei Skripal and his daughter Yulia collapse on a bench in Salisbury, poisoned by a military-grade nerve agent later identified as Novichok. This documentary reconstructs the attack hour by hour, following the police officers, doctors, and investigators who had to work out what had happened before they even knew what they were dealing with. Detective Sergeant Nick Bailey, one of the first responders to fall ill after touching the contaminated door handle, describes what exposure felt like from the inside. Medical staff at Salisbury District Hospital explain how they treated patients for an agent designed to kill within minutes, and counter-terrorism officers walk through the forensic trail that led to two Russian GRU operatives and their movements through the city caught on CCTV. The film also covers the death of Dawn Sturgess, poisoned months later by discarded perfume bottle containing the agent, and sets the local investigation against the diplomatic fallout between Britain and Russia that followed.