NCIS can be so much fun some weeks, it's sometimes easy to forget the seriousness of the jobs these special agents hold, and the sacrifice of the men and women their investigations revolve around.

Not tonight. The team grappled with a mystery that was, as DiNozzo put it, not your case du jour. For the proud members of the U.S. Marine Corps, life makes that collect call every single day.

Part I of "Engaged" was a compelling, emotionally weighty episode from beginning to end, a story moving enough to send chills up your spine even when the action on screen was minimal.

The disappearance of Gabriela Flores, an exemplary Marine by all accounts, and an even more tremendous human being, clearly hit close to home for the team, and Jethro Gibbs in particular.

Flores' unit was tasked with building and protecting a school for young girls in a war-torn province of Afghanistan were such things simply do not exist. After a RPG attack, she and others were presumed dead.

The plane transporting their remains home to Dover AFB subsequently crashed, leaving the team unable to find DNA evidences Flores was on board, despite plenty of circumstances suggesting that she was.

Gibbs took it upon himself - as a Marine himself, a leader of NCIS men and women, and especially as a father at one time - to figure out what happened and give Flores' father the closure he needed.

We learned a bit about Gibbs' past last week but tonight's flashbacks transported us to a time where Jethro became the person he is today - one who would never leave a man - or woman - behind.

Seeing a young Gibbs played by Sean Harmon, Mark's 23-year-old son, gave these scenes great authenticity, but more importantly, younger Jethro behaved just as he does now, down to the mannerisms.

I loved the way women in uniform were portrayed in this episode, past and present. Strong, equal, able and honorable. Flores was all of these things and more, making her fate that much more sickening.

To think that there are places where the mere education of girls is met by violence is profoundly upsetting. That there are Marines who put their lives at risk to change that is both humbling and inspiring.

Thanks to Gibbs' relentlessness, Flores' story may still end on a triumphant note. Refusing to close the case without iron-clad proof that this fine Marine was killed, the team kept treating her as missing.

Then they caught a break. A photo given to Gibbs by Flores' father helped ID the insurgent group that bombed the school, and thanks to McGee's video skills, we know she was abducted, not killed.

Trying to flee with children, of course. Seeing the events unfold via satellite, using night vision, was a chilling visual, but how awesome was it to see Gibbs unflinchingly headed off to bring her back.

Not that we'd expect any less, but the way this episode was set up, and feeling so connected to a victim we now know to be alive, seeing our hero rise to the occasion is enough to fill you with pride.

Time and again, Mark Harmon carries NCIS with a demeanor bold, complex and strong (like Gibbs' coffee, the Chaplain might say). Three cheers for the gray-haired grisly for his performance tonight.

The show rarely disappoints after almost 200 episodes, but this was one of those that will leave you thinking about it hours later, eagerly awaiting what will surely be a powerful conclusion next week.

There's a time and place for jokes and office shenanigans, and there's a time to get serious. In part two, Gibbs and the team will grab their gear and then some in the desert hills of South Afghanistan.

A few closing thoughts and observations before turning it over to you ...

• You know it's a long night when Abby is over-caffeinated. Think about how much Caf-Pow that takes!
• I loved Ducky's way of telling Gibbs to focus on those that are still alive. Such command of words.
• "Wheels are churning." "List of buckets." There should be a Ziva-isms Twitter account.
• Ziva's head slap of Tony, followed by Gibbs telling him to stand down, was classic.
• DiNozzo really rode a ferris wheel naked? Wait, is anyone really surprised?
• How about that first flashback in bed? Has Gibbs ever really let her go?

What did you think of tonight's NCIS? Sound off in the comments below!

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.