CSI: Crime Scene Investigation will call on an old friend as the series come to a close.

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Gil Grissom is back, and with his return comes Lady Heather Kessler (Melinda Clarke). Former dominatrix, current therapist, and Grissom's perpetual love interest, Lady Heather is ready to take on "Immortality Parts 1 & 2."

"Ladies and gents. Lady Heather Kessler is back," teased series creator Anthony E. Zuiker. "Let the world beware. After all... 'Her command is your wish.'"

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Lady Heather's final appearance will mark her seventh foray into the world of Las Vegas' premiere CSIs. First introduced way back in 2001 during "Slaves of Las Vegas," Dr. Kessler was last seen in season 11's "Unleashed."

Clarke isn't the only familiar face journeying back to set of Las Vegas' two-hour sendoff. Katherine Willows (Marg Helgenberger) and Captain Jim Brass (Paul Guilfoyle) will join Grissom and Lady Heather. It is still unknown if Nick Stokes (George Eads) will return following his season 15 exit.

Catch up with the original cast of CSI when "Immortality: Part 1" and "Immortality: Part 2" air on Sept. 27 on CBS.

Scroll through the photos below to get a behind-the-scenes look at the series finale.

Tags: CSI: Crime Scene Investigation television CBS