Veteran Homicide Detective James "Big Jim" Donegan and his partner, Detective Chris Hunter, have been called to scene of their latest case, a strangled call girl who has been put halfway through a wood chipper that was left unattended in one of the city's parks. Since he was eight years old Chris Hunter has looked up to Big Jim Donegan not merely as a mentor but also as a father-figure. Today Big Jim intends to use this case, like every other crime that they have worked together, as an opportunity to teach his technically brilliant but socially awkward partner how to be a great cop. The training, like the work, is endless. Big Jim and Chris Hunter know that they have chosen a profession that is never finished, that never stops, that death never sleeps. When they first became partners in the Major Crimes Unit, Big Jim told Chris: "People have to matter to you one way or another, even if it's only out of intellectual curiosity, but they have to count for something, inside, if you ever want to be really good on the Murder Police." Chris Hunter is doing his best to understand how people work and how to succeed on the Murder Police but the work gets even harder when two more murders, one new and one old, are added to his caseload. Of course, Chris Hunter wants to find these killers so that he can bring them to justice, but even more than that he wants to catch them for Big Jim.