A single terrible mistake cost David Hawkins everything. His marriage. His relationship with his daughter - and his career in the SAS. Now Hawkins is a man on the downward slope of life. Banished from the Regiment, relegated to a desk job at one of Britain's biggest private defence contractors, haunted by the memories of the past.

But when a talented young engineer dies in mysterious circumstances, Hawkins is sent down to Plymouth to investigate. Working alongside the company's new cyber-security expert, Alex Millar, Hawkins must find out who murdered the engineer - and why.

What begins as a straightforward case soon turns into a deadly manhunt, as Hawkins and Millar pursue their quarry from the streets of Liverpool to the Firth of Clyde, in a frantic race against time to expose a deadly conspiracy targeting the heart of the UK's defences. Win, and they'll prevent a terrifying attack. Fail, and Britain will be at the mercy of its deadliest enemy...