The first part of the CSIs crossover trilogy:
Horatio is called to find a mother's missing daughter. When her car is found near the Glades, the team searches the trees and swamps until they find a severed arm and leg. They identify the arm as belonging to the missing girl, Ashley Tanner, but the leg is discovered to be from an unidentitified Jane Doe that has radioactive sand on it only found in Las Vegas. They get a lead when they find Ashley's credit card has been used recently. Following the trail, they find another girl, Madeline Briggs, who claims she found the card on the side of a hightway. Madeline seems to be a dead end. Meanwhile, Horatio puts a call into Ray Langston who figures out the leg belongs to his missing girl, Samantha Matthews. He travels to Miami where he and Horatio work to find the killer of these girls. To their horror they discover both were seduced by the promise of making it in the world of modeling and exposed to prostitution. What they didn't count on was the fact that the girls were killed by two different men - a professional "rock star" butcher and Ashley's model manager-turned-pimp. Funding both of these men and pulling all the strings is a mysterious group called the "Zetas", crime syndicate working out of Miami, which leads Ray and Horatio to believe this is bigger than they ever thought.