NCIS may be labeled as a "procedural," but I know I'm not alone in saying what really makes it work are the characters. The plot is almost always superbly written, but only if our favorite agents can sell it.

Last week's episode dovetailed nicely with some of DiNozzo's internal struggles. This week's featured a case even more directly tied to McGee - his grandma was personally involved - and it was wonderful.

"The Penelope Papers" were heavily classified documents that got a Naval officer killed just as he was attempting to go to the press and blow the whistle on a top secret military project. His accomplice?

None other than Penelope Langston (the amazing Lily Tomlin), a character who would have been a treat on her own merit, but whose entertainment value skyrocketed because of her relationship with Tim.

Their scenes together were all terrific, especially at the end. We actually experienced a power outage with two minutes to go in the episode. Imagine if I hadn't gone back and watched the conclusion later!

Watching Penny tell Tim to reach out to his estranged dad was touching, as was the fact that he immediately did so (after seven years) as the screen faded to black. What do you think they talked about?

As far as Penny's date, I'm sure I was but one of about 20 million viewers smiling ear to ear when Ducky arrived to escort her. We can only hope this budding relationship works out for so many reasons.

Through Penny, we learned a bit about McGee's issues with his overbearing father, a Great Santini-esque individual (no, he wasn't a magician, Ziva) who always made him feel a bit inadequate growing up.

All of this made the night's mystery surrounding a secret military think tank and its robotic caterpillars - stretching the imagination a little bit there - seem secondary, but it was certainly intriguing as well.

How can your interest not be piqued when Navy Lt. Paul Booth is gunned down calling a woman later revealed to be Penny, with burns on his fingers and McGee's old card in his jacket. That's a new one!

McGee had absolutely no clue how Booth had his card from back in his fresh-faced, 15-pounds-heavier Norfolk days, and was clearly rattled by that fact. Then he traced the call, and it got 10 times weirder.

Being introduced to Penny for the first time was great because given Tim's description of his military taskmaster dad, his free-spirited, activist grandmother was the complete opposite of what we expected.

She was obviously up to something and win way over her head, but encouraged Tim - much as she loves him - not to get involved in this for his own good. Evidently she didn't know who McGee's boss is.

In 1968, Penny worked for Telles, a secret military think tank, developing The Annex Principle, which sought to essentially weaponize nature, changing the rules of the game and even life as we know it.

Their hybrid caterpillar must have been at least somewhat effective, because Penny sought to blow the whistle in 1973, only to have the Vietnam War come to an end and the project mercifully scrapped.

For whatever reason, the project is back on now, and Booth had similar reservations. He contacted Penny, one of the last surviving analysts from its original days, and they planned to expose it to the press.

The killer was not Booth's yes-man boss, as we were led to believe, but the presumed-dead director of Annex, who came out of the woodwork to make sure his mechanized caterpillar brainchild lives on!

McGee and Gibbs saved the day before he could silence Penny. Hopefully that kills the project, although we probably can't even imagine the kinds of things the military cooks up, in theory or in practice.

Between the Annex Principle, the CIA's uber-stealth training camp that spawned the P2P Killer and the Phantom Eight conspiracy, NCIS is definitely exploring the top-secret underside of government agencies lately.

Overall, "The Penelope Papers" was a typically strong episode showcasing Tomlin at her best, with a nice assist from Sean Murray (and Mark Harmon of course), a detailed murder case and plenty of smiles.

A few closing thoughts/observations before turning it over to you:

• Another favorite moment of mine? Abby jumping up and down, begging Gibbs to ask her what she found, then answering her own question before he could even reply.
• Is it ever not hilarious watching Palmer overstep boundaries at the crime scene and meeting Gibbs' icy glare? Even when you know it's coming, pure gold every time.
• Quote of the night: "Just give her what she wants." - Gibbs. "I have absolutely no idea what that is." - Palmer. "Welcome to the rest of your life, Jimbo." - Gibbs.
• Ducky had better bring Penny to Jim and Breena's wedding.
• Think Genghis Khan actually would be afraid of Gibbs?

What did you think of last night's NCIS? Comment below!

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