Four Walls

Detectives Mac Taylor, Danny Messer, Sheldon Hawkes, and Don Flack are called in to investigate a double homicide at a medium-security facility on Staten Island. Racial tensions turned the prison into a pressure cooker that finally boiled over in an all-too-lethal fashion, leaving two inmates dead. One of the killings is an open-and-shut case, complete with eyewitnesses; but the other, the murder of a former cop, defies easy answers. Initial investigation of the crime scene points to one cause of death, but the CSI team's scientific methods uncover something completely different – and wholly unexpected…