A murder case that Spencer worked on whilst at the Atomic Energy Constabulary is under review. DNA evidence that's been untestable until now looks set to reveal the murderer of two anti nuclear campaigners in the 1980s. It turns out not to be the man convicted of their deaths twenty years earlier. Meanwhile, someone inside the team is making every effort to destroy the new evidence. And all the signs are that it is Spencer himself. But events take a bizarre turn when a package for Spencer turns out to be a gas bomb which misses its intended target and renders Felix unconscious. The anti-terrorist squad puts the Cold Case team's HQ under lockdown and the team are kept quarantined until the substance that knocked out Felix can be identified. Spencer goes to apprehend the man who left his DNA at the campaigners' murder scene but is shot at and loses contact with Boyd. Boyd realizes that his investigation is being thwarted by a very powerful insider who has managed to render his team ...