NCIS: Los Angeles may be preparing to throw another curveball at the Densi relationship.

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With Kensi's (Daniela Ruah) Afghanistan arc set to wrap up in episode 19, "Spoils of War," the NCIS agent will be soon be back in California with her LAPD partner. While the duo have managed to keep their relationship afloat during their separation, episode 21 (filming as 520) could throw a wrench in their plans.

Written by David Kalstein("The Frozen Lake," "Tuhon") and titled "Three Hearts," the upcoming installment could serve to introduce Kensi's ex-fiancée, Jack.

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First mentioned during season 2, Jack was a solider who returned from Fallujah with PTSD, and despite the couple's effort to work through his disorder togeather, Jack eventually walked out on Christmas Day.

However, series creator Shane Brennan previously mentioned that the Marine might find his way back into Kensi's life sometime soon.

"Yes," Brennan said when TV Line asked if Jack would make an apperance, adding, "I answered you pretty quickly, so perhaps it's something we are already thinking about."

Whatever is set to happen in "Three Hearts," Kalstein has assured fans it will be major.

:[Kyle Harimoto] & I just turned in our script for NCISLA Ep. 520. Two words: GAME. CHANGER," Kalstein tweeted on Monday.

Do you think Jack will appear in "Three Hearts?" Tell us in the poll below!

NCIS: LA airs Tuesdays at 9 p.m. ET. Click the video below to see a preview for next week's episode, "Fish Out Of Water."