Lethal White- Robert Galbraith

When Billy, a troubled young man, comes to private eye Cormoran Strike's office to ask for his help investigating a crime he thinks he witnessed as a child. Strike is left deeply unsettled. But before Strike can question him further, Billy bolts in a panic. Trying to get to the bottom of Billy's story, Strike and Robin Ellacott — once his assistant, now a partner in the agency — set off on a twisting trail that leads them through the backstreets of London, into a secretive inner sanctum within Parliament, and to a beautiful but sinister manor house deep in the countryside.

And during this labyrinthine investigation, Strike's own life is far from straightforward : his relationship with Robin is more fraught than it ever has been — she is now invaluable to his business, but their personal relationship is much, much more tricky than that ...