NCIS: Los Angeles' agents will be plagued by a sniper during "Field of Fire."

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Callen's team will connect the dots between an extremist group and a Marine sniper in episode 22. The first piece of the series' three-part run up to the season finale, the case will call to mind one agents past.

"The team searches for a former Marine and expert sniper who escaped a veterans hospital when they discover his connection to the leader of an extremist group," CBS teased. "Also, the case reminds Kensi of her past as a sniper."

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While the sniper's motives and the nature of the extremist group are currently unclear, viewers can expect the former soldier to rain bullets down on an unsuspecting group of protesters.

"Field of Fire" will be penned by Gil Grant ("Forest for the Trees," "Windfall") and directed by Robert Florio ("Exposure," "Raven and the Swans").

In the meantime, NCIS: LA will air catch up with Arkady Kolcheck in "Beacon." Directed by Diana Valentine, episode 21 will air on April 20.

Find out more when NCIS: LA airs Mondays at 10 p.m. ET on CBS. Click the video below to see a preview for the series' latest episode, "Rage."