On a rainy November evening, trainee doctor Sasha Johnson hurries through the evening crowd in London's historic Russell Square. Out of the darkness, someone jostles her as they brush past. A moment later, Sasha stumbles, then collapses. When Detective Superintendent Duncan Kincaid and his sergeant, Doug Cullen, are called to the scene, they discover that she's been stabbed. Kincaid immediately calls in his detective wife, Gemma James, who has recently been assigned to a task force on knife crimes which are on the rise. Along with her partner, detective sergeant Melody Talbot, Gemma aids the investigation. But Sasha Johnson doesn't fit the profile of the task force's typical knife crime victim. Single, successful, career-driven, she has no history of abusive relationships or any connection to gangs. Sasha had her secrets, though, and some of them lead the detectives uncomfortably close to home. As the team unravels the victim's tangled connections, another murder raises the stakes. Kincaid, Gemma, and their colleagues must put even friendships on the line to find the killer stalking the dark streets of Bloomsbury.