"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.