Derek Powell (special guest, Sean "P.Diddy" Combs), is throwing a party on his yacht when a man and a woman come aboard and hijack the boat. They rob all the passengers but when two of the guests try to stop them, mayhem ensues and Derek's fiancee, Nadine, is shot and killed. The CSIs now have to help the man who almost stood in the way of justice during their last case. As they investigate they discover that someone went to great lengths to set up the robbery on the boat and hired someone else to shoot Nadine from the water. The evidence leads to Paul Garland, the father of the girl murdered in the previous case where Derek was defending the suspect and covering up for the real killer. Meanwhile, Delko's citizenship comes into question when his Cuban birth certificate is found on Powell's computer. He and Horatio must go to his real father, Russian mobster Alex Sharova for help even though Sharova just put out a hit on Delko.