Following on directly from the short story, Firing Line, when a cryptic series of seven symbols begin appearing across Portsmouth, etched into walls, scrawled on abandoned vehicles and even tattooed onto a murder victim, Special Branch Agent, Blake Langford is called in by DCI Heather Fordingbridge to unravel the mystery before it spirals into chaos. Alongside his colleague, Samir Khalifa, they uncover a chilling connection, each sign corresponds to an escalating act of sabotage threatening national security. As the investigation deepens, Blake turns to an old friend, Ben Broughton, a former intelligence analyst turned civilian and his wife Jade, a linguist with a shadowy past. With time running out, Blake must confront a haunting truth: the mastermind behind the signs is someone he once trusted, forcing him to weigh duty against betrayal. In a race against the final sign's deadly promise, can Blake unravel the connection and protect the people of Portsmouth in time?