'CSI's' Mark Valley: Daniel "Has a Mission to Accomplish"

Mark Valley CSI - H 2014

The evidence is in, and there's more to Mark Valley's CSI: Crime Scene Investigation character than meets the eye.

After recent stints on Crisis and Body of Proof, the former Boston Legal star joined the CBS procedural this season in a recurring capacity as Daniel Shaw, a former member of Seattle law enforcement who turned in his badge to become a private investigator. When Shaw shows up unexpectedly in Las Vegas, he's reunited with two of his former Seattle colleagues and is quickly thrown into a case from their past: the infamous Gig Harbor Killer, a serial killer D.B. Russell (Ted Danson) put away years ago — or so he thought.

Although at first blush it appears Shaw is in Vegas with good intentions — and in the pursuit of justice — the second installment in this season's long-running serial killer arc dropped a major bombshell: Shaw is working with the Gig Harbor Killer's twin brother, Paul Winthrop (played by Mark-Paul Gosselaar in a dual role).

The Hollywood Reporter caught up with Valley to discuss the latest twist and what's to come in his final two episodes of the season.

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Daniel entered this season as a private detective with ties to Russell and Finlay's past in Seattle, and all were seemingly on the same team when a former colleague — with a connection to the Gig Harbor Killer — went missing in Vegas. Now it appears Shaw is in cahoots with the Gig Harbor Killer or very possibly the killer himself. What can you tease about this next installment, "The Greater Good"?

At the end of the last episode, you find out Shaw might not have revealed to Finlay (Elisabeth Shue) everything that's going on in regards to the Gig Harbor Killer. We find out at the end of that episode that, yeah, he might be involved with the killer — just not necessarily how the audience might expect.

Could he be using the position he's in now to assist the case?

Yes. He has a couple irons in the fire. He's concerned and worried about his partner that he came looking for and has gone missing, but we find out he has another motive involved with Finlay and CSI in Las Vegas.

Shaw and Finlay's history is not only professional, but there's a clear personal connection and continued attraction there too. Do you feel it's a genuine spark, or is Shaw using her to fulfill his agenda in Vegas?

My thought is he's not really just a sociopath; he's not a person that has no conscience. But there are motives for what he's doing, and he's also conflicted. There are real feelings for Finlay, but he has a job to do. (Laughs.) He has a mission to accomplish, but he's conflicting with that.

Should Finn be worried?

She should be pulling her hair out. I think she should be worried! It's difficult for her. She has feelings for this character, and he's shown that he does, but there's also a sense he's hiding something as well. In any relationship, there's going to be some conflict and anxiety.

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The audience isn't fully aware of what his motivation is, but how much did you know about the character when you signed on for this season?

I knew I'd be playing a private detective with a history with Finn, and that I was looking for a partner who went missing. That's pretty much all I knew. I didn't know much.

So when you read the final scene in "The Twin Paradox," when the darker side of Shaw is revealed, were you at all surprised?

I had some suspicions in the beginning as to why he's there. I think in those initial scenes, it established some uncertainty. I wouldn't say to me it was a surprise. (Laughs.) But we knew something was out of the ordinary; there was something going on beyond the case.

You're no stranger to the CSI universe: You played a man responsible for killing Nick Stokes' prostitute friend in season one. As one of the few people who can say they appeared on the show during a time that it wasn't the phenomenon that it is now, and back as someone entirely new 15 years later, how would you describe your experience with CSI?

It's bloomed into this really efficient family that's really accepting of outside people and outside ideas. It's stayed fresh for as long as it has. For me it's fun to see Jorja Fox and George Eads; he's all grown up now. (Laughs.) It's been a good experience for me.

Valley's next CSI episode airs Jan. 4 on CBS.

Twitter: @ShaneSSaunders