CBS' long-running series "CSI: Crime Scene Investigation" is winding up to a close after a 15-year run and it is going to be a finale that will not disappoint.

"This will be a very satisfying ending for all the 'CSI' fans," said CBS Entertainment Chairman Nina Tassler during a TV critics' meeting. The two-hour finale will air on Sept. 27, and original cast members are expected to return for the send-off.

According to CBS, Gil Grissom (William Petersen) and Catherine Willows (Marg Helgenberger) will both make a comeback. Tassler said that the reunion was "bittersweet" for the entire team, but fans should not worry, as the franchise lives on with its latest spin-off, "CSI: Cyber." D.B. Russell (Ted Danson) is reportedly moving to the cyber department to join Academy Award-winning actress Patricia Arquette.

According to Michael Ausiello of TV Line, a major character will die in the series finale. There is no news yet as to who it is going to be, so viewers will have to tune in for more updates. What is sure, however, is that aside from Gil and Catherine, other characters will also take part in the final episode.

Old hands like Capt. Jim Brass (Paul Guilfoyle), Henry Andrews (Jon Wellner), David Hodges (Wallace Langham), Sara Sidle (Jorja Fox), Greg Sanders (Eric Szmanda), and Dr. Al Robbins (Robert David Hall) will also appear alongside newer members Morgan Brody (Elisabeth Harnois ) and Russell.

Meanwhile, George Eads, who played Nick Stokes, will reportedly not return for the finale. Stokes was the last of the original character to leave the Las Vegas department after choosing to head the San Diego lab. Elisabeth Shue, who played Julie Finlay, will also not make a final appearance.

Helgenberger recently took to social media by posting photos taken during the filming. US Magazine was quick to note that those in attendance were Petersen, Szmanda, Guilfoyle, and Fox. The "Under the Dome" actress captioned the photos, "Great fun today with this gang!"

The "CSI" series finale will air on Sept. 27 on CBS.