After learning that CSI Morgan and Ellie Brass have both been taken captive by their still unknown murder suspect, the CSIs race to piece the clues together and solve the case before it's too late. The killer, using engravings from Dante's Divine Comedy as inspiration, leaves two more bodies for the team to find, then kills their chief suspect in a fiery explosion.With only two of the Nine Circles of Hell left, the CSIs know that Morgan and Ellie will be the killer's next victims. Russell makes a break in the case when he solves an anagram that was engraved under a victim's skin, leading them to Jake and Matthew Chapman. As the CSIs race for the Chapman hideout, Morgan and Ellie manage to escape, killing Matthew in the process. However, Ellie surprises Morgan and shoots her, then lies to the cops while Morgan is unconscious in surgery. Later, Ellie kills her mother Nancy, then turns the gun on her father, Brass. Fortunately, the CSIs uncover that she was the one responsible for the murders and arrive in time to subdue and arrest Ellie.