CBS’ CSI event series has been quietly moving forward, I have learned. William Petersen and Jorja Fox are in negotiations to star in CSI: Vegas, which serves as a sequel to the mothership CSI series, CSI: Crime Scene Investigation. Casting is under way for four new characters who will join Petersen’s Gil Grissom and Fox’s Sara Sidle. Petersen also is expected to serve as an executive producer. Although CSI: Vegas has not been officially ordered, its filming is eyed to begin in the fall when COVID conditions permit for Hollywood production to safely resume.

As Deadline revealed in February when the potential CSI followup was in preliminary stages of deal-making and development, the project comes from writer Jason Tracey (Elementary), CBS TV Studios and Jerry Bruckheimer TV. The original idea was for the event series to mark the 20th anniversary of the mothership series’ premiere this coming October. That plan was thwarted by the coronavirus pandemic-related production shutdown.

With CSI: Vegas, the most watched drama series of the 21st century, CSI opens a brand new chapter in Las Vegas, the city where it all began. Facing an existential threat that could bring down the Crime Lab, a brilliant team of forensic investigators must welcome back old friends and deploy new techniques to preserve and serve justice in Sin City.

Here are details about the team of three new Vegas CSIs and the medical examiner who works with them. Of the four new main characters that will be introduced on CSI: Vegas, three are expected to be people of color.

Maxine is the new head of the Vegas Crime Lab. A former basketball coach, she is a top-flight scientist and a leader in the field of genetics. Recently divorced, she struggles with her son’s opioid addiction.

Josh is a Level III CSI who is typically the lead investigator on cases, and has a knack for crime scene reconstruction. Vegas born and bred, he comes from a family of small-time crooks and scammers.

Allie is an immigrant who followed her dreams to Las Vegas. She is a young Level II CSI with a bright future and a sunny disposition. Allie is a bonafide genius - a double Harvard whiz kid with a PhD in forensic archaeology.

Chris is an up-and-coming Level 2 CSI. He’s a private school kid who started out in a white coat and worked his way into the field. Now, he’s a lab rat set free.

Hugo took over as Head Medical Examiner three years ago. He has an endless fascination with the bodies that find their way onto his slab, and the morgue is his happy place.

Tracey executive produces CSI: Vegas with JBTV’s Bruckheimer, Jonathan Littman and KristieAnne Reed as well as CSI creator Anthony E. Zuiker and CSI: Cyber alum Craig O’Neill. Peterson and his long-time producing partner Cynthia Chvatal, who exec produced the original series, are in negotiations to return as executive producers on CSI: Vegas too.

CSI: Crime Scene Investigation, which was informally referred to as CSI: Vegas to differentiate it from spinoffs CSI: Miami and CSI: New York, followed a team of crime-scene investigators for the Las Vegas Police Department as they used physical evidence to solve murders. The original cast included Petersen, Marg Helgenberger (who is currently a series regular on another CBS series, All Rise), Fox, George Eads, Gary Dourdan and Paul Guilfoyle. Petersen was succeeded by Laurence Fishburne as CSI’s leading man. He in turn, was followed by Ted Danson.

Grissom and Sara were CSI fans’ favorite couple, whose romance was one of the most talked about storylines of the original series. Underscoring the importance of the duo’s relationship to the show and its viewers, the CSI two-hour series finale ended with the two of them sailing away together.

Petersen left CSI in Season 9. Fox departed as a series regular in Season 8. She remained a recurring guest star for the next four seasons, rejoining the cast as a series regular at the start of Season 12.

Created by Zuiker, CSI: Crime Scene Investigation has been one of CBS’ most important series of the past two decades. Launched to low expectations on October 6, 2000 on the lower-trafficked Friday night, the forensic crime drama was a breakout hit. It became the most watched series on television and established a Thursday stronghold for CBS at a time when NBC was dominating the night.

CSI: Crime Scene Investigation bowed out in 2015 after 15 seasons, having launched a $1 billion franchise for CBS that spanned four series; CSI and spinoffs CSI: Miami, CSI: New York and CSI: Cyber.