NCIS: Los Angeles will throw a "game changing" episode as viewers before they even get their season 7 sea legs.

'NCIS: LA' Season 7: Episode Title Swapped, Dave Kalstein Announces New Name For Episode 2

Writer Dave Kalstein is back, and he is ready to throw Callen (Chris O'Donnell), Sam (LL Cool J), Kensi (Daniela Ruah), and Deeks (Eric Christian Olsen) into the deep end once more. The writer took to Twitter to tease his latest episode on Monday, just a day before 702 (airing order unconfirmed) is set to head in front of cameras.

"Game-changing episode of NCISLA starts production tomorrow! See you on set @ 6:30 AM," Kalstein wrote.

'NCIS: LA' Season 7: Premiere Title Announced, Will Tony DiNozzo Really Feature?

Titled "Citidel," the upcoming episode is primed to introduce long-time fans to a highly anticipated character.

"Tech scouting ep#702," production manager Rick Tunell teased on Friday. "You'll meet someone you've been wanting to meet. #ncisla."

It's currently unknown who will pop up in Kalstein's new story, but we have some ideas. The truth about Callen's father has been the driving mystery since day 1, and although G thinks the man he spent his life searching for is six feet under, the final moments of the season 6 finale may indicate otherwise. Meanwhile, Deeks' mother was supposed to be introduced back in season 5, but plans were changed when Daniela Ruah became pregnant and the Afghanistan storyline was developed.

Stay tuned for more updates - and hopefully a concrete answer - as filming continues. NCIS: LA will return to CBS on Sept. 21 at 10 p.m. ET. Click the video below to see a clip from the series' most recent episode.