Former CSI and current FBI agent Catherine Willows will return to Las Vegas to investigate an explosive attack at her co-owned Eclipse casino, but it will be the prime suspect in that catastrophe that brings Gil Grissom back to town after six years.
Lady Heather (Melinda Clarke) winds up at the center of Catherine (Marg Helgenberger) and CSI's investigation, according to TV Guide magazine. The dominatrix-turned-sex therapist will likely call on Grissom (William Petersen) to clear her name given that he has always looked out for her best interest in the past.
The CBS drama will end its 15-season run with a two-part series finale titled "Immortality" on Sept. 27. The episode will unite "CSI" stars past and present including Helgenberger, Petersen, Paul Guilfoyle (Capt. Jim Brass), Jorja Fox (Sara Sidle), Eric Szmanda (Greg Sanders), Ted Danson (D.B. Russell), Wallace Langham (David Hodges), Elisabeth Harnois (Morgan Brody), Robert David Hall (Dr. Al Robbins), David Berman (David Phillips) and Jon Wellner (Henry Andrews).
George Eads and Elisabeth Shue chose not to reprise their roles as Nick Stokes and Julie Finley, respectively.
"It's a privilege to be able to bring real closure to this show - something that rarely happens when a program gets canceled," creator Anthony Zuiker told TV Guide. "Our finale is scary and thrilling and entertaining as hell, but it's also a chance to thank the fans for their undying devotion."
Zuiker added that he wants everyone to "feel good" about where their favorite characters end up, but that may not happen for those GSR 'shippers still hoping divorced couple Grissom and Sara can rekindle their love.
"Can we please everybody with this finale? Of course not," he said. "But will we please most of the people and give them the emotional experience they want? Absolutely."
A new first look photo from Entertainment Weekly shows Grissom and Sara at least working together as they search for clues alongside their former colleague Catherine. Petersen, who left the show in 2009, was happy that he and his co-stars could return for one last final hurrah.
"I'm so glad we were able to do this, to go and be with the crew and the cast again, to be able to say goodbye," he told Entertainment Weekly. "It was really a big to-do for us."
The two-hour series finale of "CSI" will air on Sunday, Sept. 27 at 9 p.m. on CBS.
