With a mole in their midst, Horatio and Calleigh head a team of elite Crime Scene Investigators as they enter their most challenging season yet.

Under the roof of a state-of-the-art redesigned crime lab, the dynamic duo investigate a series of crimes including a night-club murder, the death of a pool boy, a cold case rape, and a murder with a double-jeopardy clause, all whilst under the scrutiny of an anonymous mole, and facing a series of cases that threaten the team.

With Alexx accused of murdering a child molester, Horatio accused of murdering an innocent woman, Wolfe facing the loss of his eye, and Mac Taylor joining the team when a prisoner transfer goes awry, it's ultimately Delko who faces the greatest loss: his sister who was to marry Horatio is gunned down by the Mala Noche gang in an attack that will begin a narrative recurring throughout the next several seasons.

A convicted serial killer escapes after sabotaging an airplane that was flying him from New York to Miami, where he allegedly buried a body.

After fleeing the crash site, the man goes on a killing spree and abducts a college student.