'NCIS: Los Angeles' Star Daniela Ruah Previews Kensi's 'Suicide' Mission — Watch the 'Intense' Sneak Peek!

Brace your Deeks and Kensi loving hearts!

Brace your Deeks and Kensi loving hearts!

Kensi is gearing up for her most intense mission yet on this Sunday's all-new episode of NCIS: Los Angeles -- and only ET has your first look at the hour's most heartbreaking moment and exclusive scoop from star Daniela Ruah.

"Kensi gets called in for a mission that is quite secretive," Ruah tells us ahead of the action-packed episode. "She's called in by herself because an ex-boyfriend from about ten years ago, whom she hasn’t spoken to since then, decides to take over a nuclear launch facility, so they're hoping that [Kensi] can talk this guy down from doing what he's about to and fire these nuclear weapons."

"Essentially, it could be a suicide mission," the actress adds.

"It's pretty intense, because Deeks doesn't want her to do it and he wants her to come home," she says. "He's like, 'Let somebody else do it!' and she's like, 'I can't. I'm here, I can do this, I can save people,' and so they actually end up having a really, really intense conversation."

ET has your first look at that emotionally-charged phone call between Kensi and Deeks in the sneak peek clip above, but we've got to warn you -- it's pretty tearjerking to watch!

"I think the audience is going to enjoy the ride," Ruah concludes. "It's a dark and intense episode, but I think people will be on the edge of their seats for sure."

NCIS: Los Angeles airs Sundays at 9 p.m. ET/PT on CBS.