The squad will be asked to man the investigation regarding a murdered Drug Enforcement Agency (DEA) agent in the upcoming episode of the CBS procedural series "NCIS: Los Angeles."

In "Citadel," Cartermatt reports that a former operative from the drug enforcement agency who has previously worked with the Los Angeles team will return to seek for help. Talia Del Campo's (Mercedes Masöhn) partner was killed while on the job, and she needs experts to flush out the killer. With things starting to look better for Callen (Chris O'Donnell), the department can now afford to focus on other important cases, just like solving a murder incident.

Last episode, the boys were busy getting Callen back into the fold. Sam (LL Cool J) and the rest of the gang were worried about him when he decided to embark on a secret project involving his father. Last season, Callen discovered that Hetty (Linda Hunt) lied to him about his parent, claiming he was already dead. The shocking truth would then prompt him to launch his own investigation to locate his father, while going rogue in the process.

Meanwhile, Deeks (Eric Christian Olsen) will surprise Kensi (Daniela Ruah) by introducing her to his mother (Pamela Reed). The latter has been steadily worrying that Deeks is hiding something from her. It turns out she need not be concerned, as he is only setting up a meeting with his mother.

Ruah has previously revealed to TV Line that Deeks and her character would be taking their relationship to the next level for season 7. She said that things must be getting serious between the two once Deeks involved his mom in the picture.

"Throughout that episode, Deeks gets calls on his phone, he doesn't tell Kensi who it is, he doesn't pick up... so you can see he's making the decision about whether he wants to take this step or not," the actress said. 

"NCIS: Los Angeles" airs Mondays at 10 p.m. EST on CBS.