The episode begins with an explosion at a warehouse party that leads Horatio Caine and his team to investigate a man hired to build dirty bombs for terrorists. While processing the scene, Horatio discovers a bloody fingerprint belonging to his brother, , whom he previously believed was dead. As the investigation progresses:

faces a life-threatening encounter in her ballistics lab when an unknown assailant holds a gun to her head, leaving her to question her future as a CSI.

emerges from deep undercover after his son is kidnapped, forcing the estranged brothers to work together to rescue the boy.

The episode serves as a major turning point for the series, revealing that Raymond is alive and setting up long-term character arcs for Horatio and Calleigh. 10-7 | CSI | Fandom