NCIS: Los Angeles' Marty Deeks will have a tough choice to make while Kensi is abroad.

After nearly five seasons of working together, the LAPD Detective and his partner finally reached a place in their relationship where they have decided to address their romantic feelings for each other. Unfortunately for the new couple, Kensi (Daniela Ruah) was reassigned to Afghanistan hours later, and while she's away, Deeks (Eric Christian Olsen) will have his feelings tested during an upcoming case.

"515 spoiler: Deeks works a case with someone who challenges his feelings. Will he stay true. #staytuned #NCISLA," teased executive producer John Peter Kousakis in a recent tweet.

The problem may be caused by the presence of Mercede Masohn's character. Kousakis confirmed the 666 Park Avenue actress' involvement in "Fish Out of Water" and the actress has recently tweeted several pictures from set (see gallery above).

"I am having SO much fun on the set of @NCISLA_CBS Thank you [Chris O'Donnell] and [LL Cool J] and [Eric Christian Olsen] #FunTimes!" Masohn tweeted when filming began last week.

In the mean time, Kensi will be stepping up her game as she tries to track down the White Ghost.

"2014 spoiler: Kensi gets serious about her mission in Afghanistan. Her plan to capture the White ghost is bold! #NCISLA," Kousakis teased via Twitter.

NCIS: LA airs Tuesdays at 9 p.m. ET on CBS. Click the video below to check out Deeks and Kensi's surprise Christmas conversation.