While Calleigh and Ryan are investigating a dead body in the attic of a foreclosed home, they are caught of guard by a shooter who opens fire on the attic floor and sets the house on fire with an improvised bomb. After narrowly escaping the fire, with the dead body, the team sets out to find the person who tried to destroy the crime scene and our CSIs.
Shortly following her return to work, Calleigh suffers a delayed reaction to the smoke inhalation and is rushed to the hospital where Alexx Wood, a part-time doctor on staff, manages to save her life. After determining the attic victim was a surgeon, Dr. Donald Phelps, and was addicted to heroine, evidence reveals his drug dealer set the house on fire so Calleigh and Ryan wouldn't find his stash. But when evidence proves the drug dealer didn't kill Phelps, and the team discovers Phelps was performing illegal surgeries in his garage, the case takes a turn into the world of black market organ transplants.