It's time for NCIS: Los Angeles' Callen to resume the search for his father.

The Special Projects team will head to Mother Russia in the season 6 finale, and a trip to Moscow during "Chernoff, K" will allow Callen (Chris O'Donnell) to delve into his mysterious past once more.

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"An ongoing case leads Callen,Sam (LL COOL J), Deeks (Eric Christian Olsen) and Kensi (Daniela Ruah) to Moscow, where the team must assume multiple undercover identities to locate their suspects," CBS teased of the May 18 episode. "Also, Callen uncovers new information regarding his father."

The Russian story line will kick off in "Beacon" when Arkady Kolcheck (Vyto Ruginis) reenters the picture, kicking off a case the will change everything. A three-episode arc that will begin with "Field of Fire" and end with "Chernoff, K" will follow.

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Callen has not made any inquires into his past for over a season and a half. The series' 100th episode, "Reznikov, N," resulted in a deluge of information for the orphan, finally giving Callen his father's name and location circa 1974. Since then, however, the orphan's life-long quest has stagnated.

Find out what Callen will learn next when NCIS: LA airs Mondays at 10 p.m. ET on CBS. Click the video below to see a preview for the series' next episode, "Beacon."

Tags: NCIS: LA NCIS: Los Angeles television CBS