S4, E25: Horatio and Delko search Miami to bring down the Mala Noche gang once and for all after the murder of someone very close to them. However, their quest is jeopardized when the Feds seize the CSI lab with the intent to close it for good, based on the tip from the mole inside. When the mole is finally revealed to the entire lab, the news sends the remaining CSIs reeling.