How do you stop a terrorist who's already behind bars, and whose reach goes far beyond the walls of a maximum security prison? Send in LL Cool J, obviously.

Sam goes undercover as a prisoner to track down a terrorist group responsible for major bombings around the world on the next episode of NCIS: Los Angeles.

"Lockup" also features the return of Peter Cambor's Dr. Nate Getz, who left to take part in an unexplained mission during the second season premiere.

Here's the promo for next Tuesday's NCIS: LA:

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