Callen (Chris O'Donnell) goes undercover in a mental health hospital when "NCIS: Los Angeles" season 8 returns to the small screen with episode 7, "Crazy Train."

CBS is keeping its cards close to its chest on this episode as it only mentions Callen's goings-on, which involves him posing as a mental patient to get to the bottom of a National Security Agency (NSA) agent's disappearance.

The person in question went missing in the midst of his efforts to track an ISIS cell that is trying to cross the Mexican border. The "NCIS: LA" season 8 episode 7 promo teases that Callen will be in some serious watery trouble as he goes about the mission.

At some point during his undercover operation, he is caught by a group of men who have a rather sadistic idea of fishing and used Callen as bait to a couple of sharks.

His knowledge of punching the creatures in the nose and grabbing the gills to survive an attack, which he recites to himself in the upcoming episode's promo, as the sharks drew closer may not be enough to save him.

Making things worse is that he lost contact with his team back home. Now, it is up to Callen to do the impossible and save himself in the face of this danger.

A promotional still from the episode shows Sam (LL Cool J) survey the location Callen was thrown into, so it looks like Callen might not be completely alone in this.

Despite the focus on Callen's mission, "NCIS: LA" season 8 episode 7 is still expected to touch on Deeks (Eric Christian Olsen) and Kensi's (Daniela Ruah) situation.

In the previous episode, the latter has learned that she may not be able to walk again, leading her to push Deeks away. Fans are hoping that it will not be the end of the road for the two.

Deeks has proven that he wants to be with Kensi no matter what, and if she just lets him in, they could be in this and get through this together.

"NCIS: LA" season 8 episode 7, "Crazy Train," will air on Sunday, Nov. 6, at 8 p.m. ET on CBS.