Something big is brewing on the set of NCIS: Los Angeles.

The upcoming premiere is set to introduce a turbulent storyline of change amongst the characters, but it appears writers will be adding even more drama, as they are currently laying out some major bombshells for midseason.

"My next NCISLA script will be the finale of November sweeps season (Episode 509). It'll be epic and yes... It. Will. Change. Everything," tweeted Dave Kalstein, a long time series writer.

While still untitled, the episode will be directed by Executive Producer John P. Kousakis. For his part, Kousakis seems excited to be directing a few select scenes, although it is unknown if they will be from the Kalstein installment.

"Today's tease...I'll be directing some undisclosed scenes which will impact a major part of S5. #staytuned #NCISLA #BestCrewInHollywood," Kousakis told his followers last week.

Kousakis is also busy scouting locations for an Afgan storyline that will enter into play midseason, a project he has referred to as "Blue Cloud." Photos posted by production manager Rick Tunell on the same day that Kousakis finished scouting show ideal spots for the Middle Eastern location. While there is no official word on which episode these locations will be featured in, Tunell noted that Kousakis will be directing from these areas, meaning they may be used in episode 9.

Could the Afghanistan storyline be related to the impending departure of a team member? Deeks (Eric Christian Olsen) will receive some surprising news around the same time as the Kalstein episode while the series has yet to reveal how they will work Daniela Ruah's real-life pregnancy into the program.

"Sunday spoiler: Deeks will be surprised by a Hetty decision he never saw coming. Mid-season. #watchforclues #NCISLA #thisS5willRock," Kousakis tweeted.

Fans will have to wait to see if any of these puzzle pieces happen to align.

NCIS: LA returns to CBS on Sept. 24.