A plot is uncovered to attack major cities in the UK with chemical weapons. A terrorist cell discovers the dump site of thousands of mustard gas shells, which were disposed of following the Second World War. During the sinister salvage operation, an undersea explosion releases a cloud of blister agent which envelopes the riverside areas of Liverpool creating carnage. John Tankersley and the Terrorist Taskforce have a desperate fight on their hands to limit the damage and stop any further attacks.