The gang is back for the CSI finale. Marg Helgenberger has tweeted behind-the scenes pics from the set of the 2-hour CSI: Crime Scene Investigation finale, which will air on Sunday, September 27. Above is Helgenberger with fellow original star William Petersen. Helgenberger’s second tweet below shows five original characters: Catherine Willows (Helgenberger), Dr. Gil Grissom (Petersen), Sara Sidle (Jorja Fox), Greg Sanders (Eric Szmanda), and Jim Brass (Paul Guilfoyle).

Anthony Zuiker-created CSI has been one of CBS’ most important series of the past two decades. It is bowing out after 15 seasons and three spinoffs.