Exclusive CSI Sneak Peek: Battlestar's James Callis 'Bugs' Stokes -- Plus: More Finale Preview

CSI Season 13 Finale PreviewBattlestar Galactica alum James Callis is stirring up trouble again, this time on CBS’ CSI (Wednesday, 10/9c) – and TVLine has a first look at his investigative journalist “bugging” Nick Stokes (and in doing so, setting the stage for a Gil Grissom shout-out).

Callis, but one of a flurry of familiar faces popping up in the long-running procedural’s Season 13 finale, guest-stars as John Merchiston, “a Vanity Fair-style journalist who comes to Vegas to do a story on the crime lab,” showrunner Don McGill tells TVLIne. “The desire of the LVPD is to get a little positive PR, since there’s been so much negative publicity regarding police corruption over this half year. But pretty quickly we see that he’s kind of a smartass and his agenda may be a little more aggressive and mud-raking” in nature.

That said, though the journo ruffle’s feathers at first, “Russell starts to appreciate the reporter’s smarts and insight” as the episode unspools.

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In this exclusive clip from Wednesday’s finale, as Merchiston shadows Stokes for a bit, something doesn’t smell quite right. Press PLAY for the sneak peek, then scroll down for more preview.

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The Case of the Week revolves around “a pretty wily serial killer who is targeting prostitutes and sex industry workers in Vegas,” McGill shares. That tees up other guest stars such as Tim Matheson (Burn Notice, Hart of Dixie) as “a hard-line solicitor of escorts and, we suspect, possibly our serial killer. He’s a man of science, a collector of art and a wolf in very thin sheep’s clothing,” says McGill.

Eric Roberts (Star 80, Crash) shows up as a preacher at comely Miss Kitty’s church, while Ozzy Osbourne rocks a scene or two (and even performs) when D.B. meets up with Callis’ character Skin in the Gameas he wraps a piece on Black Sabbath’s new concert tour. “We heard that Black Sabbath was interested in doing CSI and so we were very, very excited,” McGill says. “Since they’re debuting their 13th album, it’s a perfect match for our Season 13 finale.”

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Elsewhere during the hour, since the case involves Sin City’s sex trade, “One of our CSIs gets the smart and dangerous idea of volunteering to pose as a prostitute to lure the killer out into the open — with the results being some jeopardy,” McGill teases.

As Season 13 draws to a close, “We’ll see one of our CSIs in danger and we will find that one of our CSIs’ family members is also in danger,” McGill says, hinting that Annabella Sciorra (Law & Order: CI), guesting as Captain Brass’ wife, could figure into the latter dire scenario.

“We thought it would be interesting to do a sort of parallel storyline where a family member of one of our team and someone within the team simultaneously find themselves in jeopardy,” McGill explains. “It seemed like the right way to end a season where we’re really exploring all the tension within the CSI family.”