PCs Quinnan and Stamp are first on the scene of a major chemical spill when a tanker truck hits some scaffolding near the Sun Hill tube station. Insp. Monroe arrives to supervise the evacuation of the area, as the fire department try to work out what chemical has been spilt, although a lack of documentation on the truck makes this difficult. The driver dies in hospital, but when his wife in informed by Uniform, she doesn't seem very upset. Further investigation reveals she is behind a scheme to provide unlicenced or disqualified drivers to the trucking company.