In the closing moments of last week's episode, Rebecca Nevins (Christina Chang), Delko's boss and the former girlfriend of Horatio (David Caruso), was killed by a car explosion just before Delko could report the new leads he found while trying to track down who stole diamonds from the evidence locker.
In Monday's episode (10/9c on CBS), the person responsible for the theft and the bombing will be revealed, and there will be dire consequences.
"[The explosion] kicks Delko's investigation into overdrive," producer Krystal Houghton tells TVGuide.com. "It's not just who's stealing, but who's murdering? During the investigation, somebody involved in the theft dies, and somebody else's career is ruined. Unless there's a prison break, it's safe to say we've seen the last of him."
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But how many bridges will Delko (Adam Rodriguez) burn as he investigates? In the last episode, Walter Simmons (Omar Miller) didn't take very kindly to Delko snooping into his bank account. Natalia (Eva Larue) has also had tense words with Delko, and she will ultimately reveal Delko's investigation.
"Natalia feels betrayed by Delko," Houghton says. "She knows what happens when you're the mole and keep secrets, so she wants to be up-front. She promised him she wouldn't tell, but there's only so long that she can keep that promise."
But Delko's relationship with girlfriend and CSI Calleigh (Emily Procter) could be the most damaged. "He's her boyfriend, but he's also investigating her," Houghton says. "That's going to be a tough one if she finds that out. He keeps it a secret, and he puts his job above the relationship. That's a big issue for them."
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Whatever bad blood might exist after Delko takes down the responsible party — and Houghton is confident the audience will be surprised — the team will have to find a way to forgive him. In the season finale (Monday, May 24 at 10/9c), a serial killer taunts the team with clues to his victims, and ultimately, Delko is one of the few who will be able to save the CSI team.
"This killer is out for blood, and all the CSIs end up in jeopardy, except for Horatio and Delko," Houghton says. "The killer has very sneaky ways of getting to people — he doesn't even have to be there. He sets things up ahead of time, and it's a ticking clock for the CSIs to stop him. What they don't know is that he set up one of these ticking clocks in their lab."