CSI: Vegas returns to the scene of the crime with original stars William Petersen and Jorja Fox reprising their characters, Gil Grissom and Sara Sidle respectively, after more than six years following the end of the show’s initial run. The beloved CBS franchise kickstarts the new iteration with a mix of the old and the new, bringing back Grissom and Sara back to the Crime Lab when former homicide detective Jim Brass gets caught up in a scandal that could bring down decades of case work they’ve done.

“There is a tremendous amount of anticipation. There would be under normal circumstances, but certainly we’ve been talking about this since 2019, and here we are in 2021,” Fox told ET over the phone on Tuesday. The original plan, according to the actress, was for the revival to launch on the 20th anniversary last Oct. 6. “I’m excited and I’m just hoping there’s an audience out there who’s going to want to watch.”

A lot has changed – and, in many ways, hasn’t changed – when Grissom and Sara step back into the the world of crime-solving. After years away from the grittiness of Sin City investigations, the couple is back to do what they do best. Seek the truth with the help of science and forensics. For Fox, even getting the chance to revisit the character of Sara is a “phenomenally rare” opportunity, one she doesn’t take lightly.

“As an actor, it is absolutely exhilarating to play a character for a longer period of time, especially if it’s a character that you like or that you resonate with. And I love Sara. Sara Sidle is my favorite character I’ve ever played,” she said. “There’s so many reasons to love her. I love that she’s flawed. I love sometimes that she’s not the most popular person in the room, but she always sticks to her heart and her beliefs. One of the most exciting parts for me of coming back, was there’s been this longstanding love affair between Gil Grissom and Sara Sidle. It’s 21 years old. It’s as old as the series itself. It’s been on again, it’s been off again. They’ve been separated, they’ve been married, they’ve been divorced. And we haven’t seen very much of any of that on screen.”

“As we begin these 10 episodes, Sara and Grissom return to Las Vegas and they return together as a couple,” Fox confirmed. “We’ll be playing that relationship way more than we ever did before. That was really fun for me. It was also unprecedented. I didn’t expect it to be really in the script because it never was before. So that’s been really fun. The second part of why it’s been exciting to come back is, and not necessarily for a good reason, I think when the show started in 2000, the world seemed very topsy-turvy. There was a contested presidential election, whether there should be a recount or not. There was the Supreme Court that decided that they could pick a president, which I think is absolutely wrong. And here we are. I never would’ve thought that in 2021, the world would be even more topsy-turvy than it was 21 years ago, and it is. Because the show is so much about truth, finding the truth and using science to find the truth, it’s super exciting to be back and in a very appropriate time for the show to be back.”

To kick off the franchise’s return ahead of Wednesday’s premiere, Fox discusses exploring Sara and Grissom’s relationship, the biggest difference with her character now compared to what viewers knew of her then and her favorite Easter egg for longtime fans of the show.

ET: What can viewers expect in CSI: Vegas as we get to peel back the curtain in terms of that relationship? Because, like you said, whatever they did out of the office, so to speak, wasn’t exactly a priority to explore necessarily something that we didn’t really see a lot of.

Jorja Fox: The show, at its heart is it’s a procedural show. It was really designed in 2000 that you can sit down and watch an episode and you didn’t have to see the episodes that came before. You didn’t have to worry about the episodes that came after. I think five, six years in television and streaming, we’ve seen a return to a line of a story that carries through multiple episodes. We’ve seen a real return to character-driven stories. It is so much about the characters. Both of those things are two of [showrunner] Jason Tracey’s real strengths. And he decided to go for that. It’s not only Sara and Grissom we’ll see weaved in and out of these 10 episodes, but we’re going to have this crime that is also going to follow the whole storyline and hopefully the audience will want to take the journey with us in trying to unravel what happened. The stakes are so high and it ultimately involves both Sara and Grissom and this amazing new cast that Jason Tracey has brought to the show. We join forces to try and get to the truth.

What is Sara like in 2021 versus what we knew of her then? What is the biggest difference in your mind?

At least initially, when the story opens, we’re going to see like a lighter, upbeat Sara Sidle. Being away from the Crime Lab for five years and being away from all the things in Las Vegas that were part of her daily life, which is a lot of violence and a lot of death… being away from that for five years, she’s effervescent and fun. We’ll see her like that in a way that we didn’t get to see that much in the length of CSI: Crime Scene Investigation. That is, until things take a dark turn, which invariably they do.

How was it marrying the old with the new, and what was it like for you getting to reintroduce this world but also have new blood?

Well, Matt [Lauria] and Mandeep [Dhillon] and Paula [Newsome] and Mel [Rodriguez], they are electric. They are mesmerizing. The characters themselves are multi-dimensional. There’s a lot of humor in this new series, which we did in the old series as well, but right out the gate, again, Jason Tracey has hired a group of actors that really excel in comedy. Of course, it’s 2021. I think in 2000, I thought that, “Wow, we’re on the cutting edge of science. Isn’t this just amazing?” 2021 makes the science of 2000 look kind of simple and like Sesame Street. We’re going to be able to take that to a whole new level. These actors that are part of the show are so good at being smart and opening the door for an audience to get to learn about this stuff and to get to follow these cases. The cases are really dark and fun and twisted, and I think another thing that was pretty difficult for CSI: Vegas to do is to come up with cases that we’d never seen before. You know, over 300 cases on CSI: Crime Scene Investigation, and then you had all these other CSIs out there that were doing these cases every week, too. That has been a huge challenge for the writers. And I feel like they’re magicians. The magic that they’re doing at creating stories that’ll be new, not only are they good, but I think that CSI fans are going to really enjoy going to different dark places that they haven’t been before with these really cool characters.

There is a gap in time with what Sara’s been up to in these years between. The first episode dropped a few hints here and there about her career and personal life decisions. Was it a treat for you to address some of those questions longtime viewers may have about what she’s been up to?

It was an absolute treat. I’ve always thought the story of Sara and Grissom and where they’ve been for the last five years, to me, would also have made a really fun show, partly because I do love science and I love traveling the world. And the last five years or so they’ve been living on a boat, they’ve been traveling the world, they’ve been working for marine mammal conservation and marine habitat conservation, and I think that story is a show that I would actually watch. It was really great to drop some of those pieces. I think it would be fun, even, to tell more of those stories. We’re also going to get to see where has Jim Brass been and where has David Hodges been? Those stories are fascinating, too. I think there’ll be some surprises in there for all four of these characters that were part of the original show. There’s definitely surprises for the audience about where they’ve been and what they’ve been doing.

It only seems natural that the question of whether other original cast members will pop back in later on in the season comes up. Are there more surprises in store in terms of familiar faces?

I would love to see the old crew again, and I’m not going to answer that question. I want everybody to tune in and watch, but I certainly hope so!

What do you want people to take away when they sit down and watch the show, whether they’ve been a longtime viewer or just dropping in now?

There’s a couple of things. That love can prevail and love can last. Anybody who manages to make a love affair work for 21 years through all kinds of stuff, I think that’s really cool and really interesting. The other thing is that science is really cool and that science can really help us not only navigate crimes and the worst day of people’s lives, it can help us solve so many of the questions that are pressing so very hard on us right now. The Earth does not have time. We’re out of time and science can really help us with that. I hope that invigorates people’s excitement and belief in science.

It’s been a while. That rush is something as an actor, it’s the greatest feeling that you can have is to have a piece of work that is going to air and that there’s an audience that is already probably going to check it out. That’s the upside is you already have a little bit of an audience there. The scary part is, is it going to be good enough for that audience that followed the show for so long, were such amazing fans? We made this thing for you and for everybody that loved the show. I think expectations will be a little higher and they’re always, for me, a little higher. Something that I’ve already loved and I’m going to see again, my expectations are a little higher than if I was going to watch something that was brand new, that I didn’t really have a history with. It’s a thrill.