The victim is a woman who has a connection to Sam's time in the military, but as Callen (Chris O'Donnell) and the rest of the team work to clear his name, they uncover some tidbits about Sam's past — and start to question if it's possible that he's not innocent after all.
"We say, 'There's just no way,'" O'Donnell, who directed the episode, tells TVGuide.com. "But then, as they take him away and we start to investigate, we find out that his DNA is all over the crime scene and there's a lot of evidence pointing in his direction. Obviously this becomes very personal for the team, trying to defend one of our own."
For O'Donnell, stepping behind the camera came with its own challenges, but was an opportunity he embraced.
"For me, it's such a great way to mix up the season," he says. "To suddenly get involved behind the camera and work with half of our crew who I don't see on a day-to-day basis — the people that are building the sets and scouting the locations and that sort of thing — that's great. And I particularly love the post-production aspect of it, getting into the editing room and being able to have an impact on making sure that the beats that were important to me when I read the script, and that I think helped to tell the story, get in. ... It just gives you great appreciation for how hard everyone's working, because it's really easy sometimes to sit back as an actor to sit back and think, 'Well, why am I waiting? Why aren't we rolling right now?' It's like, well, you know, a lot of people are working on this and a lot of things had to come together for this to work so smoothly. It's easy to take that for granted.
"I love having an episode that has to do with Sam stuff as well," O'Donnell adds, "because it just gives me a chance to boss around [LL Cool J] all day, which is really fun for me."
Though he assures that fans shouldn't be concerned about Callen and Sam's friendship being in jeopardy, O'Donnell says the incident does make Callen see his partner in a new light.
"Hetty and Sam are really the only family that Callen has in the world," he notes. "Having that companionship and having someone who is busting your chops and you can give a hard time to all the time, it's a great friendship. And when somebody you're that close to is brought up on charges of murder and you start to investigate and look into the evidence, and it's all pointing to him, and it's stuff that's hard to refute, it's DNA, it really challenges your level of trust and your belief in whether or not someone would be capable of doing something like that."
The episode also features an intense fight scene involving Sam that O'Donnell calls "one of the best ones we've ever done, in kind of an unusual location, to say the least."
Check out a sneak peek from the episode below:
NCIS: Los Angeles airs Mondays at 10/9c on CBS.
(Full disclosure: TVGuide.com is owned by CBS.)