The mysterious Dr. Jekyll serial killer hasn't shown up lately on CSI, but the show's producers haven't forgotten about him — and neither has Ray Langston.Laurence Fishburne) comes across a familiar name: Nate Haskell. "It's just a little callback to him, which is kind of eerie and could be a sign of things to come," Tom Mularz, who wrote the episode, tells TVGuide.com.Haskell (Bill Irwin), of course, is better known as the Dick & Jane killer, who was first introduced in the Season 9 episodes that brought Langston onto the team. Executive producer Carol Mendelsohn says Haskell may have a connection to Dr. Jekyll, which reinvigorates Langston through the rest of the season in his hunt to bring Jekyll down."Dr. Jekyll isn't done killing people," Mendelsohn says. "We will not only see more victims of Dr. Jekyll, but we will begin to see and unravel the obsession that Ray Langston has for catching him. He is hot on his trail, and nothing will stop Langston. It will drive the end of our season."Jorja Fox) handled before leaving for Costa Rica. It was one of the things that kind of frustrated her to the point of wanting to leave," Mularz says, adding that it's interesting for Langston to see someone share his passion about closing a case. "Langston, who joined the team after that, has really only known her as Mrs. Grissom. So he gets a glimpse of the fire that still lingers around some of these cases in her mind."As Langston gets closer to Dr. Jekyll, Mendelsohn says that Langston's chase will be literal. That more physical side to Langston will also come out in Thursday's episode, according to Mularz. "We get to see him run into a burning building and crash through a door," he says. "It's nice to see him in that kind of action mode after we've seen him do these brilliant mental tasks."Will Langston's efforts pay off? "Dr. Jekyll and Langston may be headed for a final confrontation," Mendelsohn says, "and I do not think Ray Langston will end up unscathed."