Comparing NCIS episodes can be a difficult task, since almost all of them range from very good to excellent, but this one definitely falls into the latter category. "Enemy on the Hill" had it all.

DiNozzo was at his clowning, and investigative best. He may want to lay off the caffeine for his health, but being even more wired than usual didn't hinder his ability to crack the case, or crack us up.

Serving as his foil or directly engaging him, McGee was by his side throughout. Ziva actually got to rough some people up. Gibbs, once again, served as the team leader in more ways than one.

Most significantly, Abby made a discovery that rocked her world, but warmed our hearts.

The fact that Abby would donate a kidney - not blood, not bone marrow, but a kidney - to a stranger just for the pure goodness of it somehow didn't surprise me. Okay, it did, but if I had to select one television character who could believably think up such an idea, Abby Scuito would top the list.

The consequences of such a decision, such as the risk of any major surgery and long recovery time, did not faze her in the least. But she wasn't prepared for one shocking result.

How could she be? When another exact match turned up as a donor - one also doing so out of the goodness of his heart, fittingly - Abbs realized the impossible. They're related.

The actor who played Kyle, Daniel Louis Rivas, was superbly cast (and used to date Pauley Perrette, according to at least one online source, if you can believe that one).

Between their facial resemblance and the way the actors played off each other, that scene was both wonderful, in that he is obviously just the type of awesome human being who could be Abby's brother, and sad in the sense that it only led to more unanswered questions for our girl.

That's when it hit her. Her parents never gave a child up for adoption, but ...

Someone else's did. Her biological parents. Coming to grips that she's adopted - confirmed by a DNA test on her mother's hair - was understandably upsetting for Abby, or at least left her reeling. But there to reassure her and remind her of true meaning of family was her rock, and father figure, Gibbs.

Anyone would be thrown for a loop by this revelation, but for such an openly emotional person, you just know it will be particularly hard on poor Abby. Hopefully she comes to grips with it down the road, through some soul searching and perhaps by reaching out to Kyle again.

No matter what, she has Gibbs and the NCIS team. That's no small factor.

This episode was the third in a row to conclude on a touching note, having explored the past of one of the characters and unearthed a difficult subject. All have been very well done, relegating the night's caper to secondary status. That said, the mystery on "Enemy on the Hill" was a good one.

The killer dying in the first minute was a different wrinkle.

Instead of a manhunt for a wanted assassin, the team (with Metro PD Det. Sportelli) were tracking the person who solicited his services, believing he was going to murder Lt. Commander Geoffrey Brett.

As legislative fellow to the House Armed Service Committee, Brett was influential with overseas government contracts - a fact that played a role in his actions later, but wasn't why he was wanted dead.

His accountant, Drew Turner, wired money to an account under the name of George Kaplan, to paid 25 grand for the hit on Brett. Only Kaplan was a bogus individual ... crafted by Brett and Turner.

It turns out the attractive, female accountant created the Kaplan account to help Brett receive kickbacks from companies he helped secure government contracts. This was secretive and very illegal.

Turner wanted Brett dead because she needed the money to pay off her gambling debts. Brett found out she ordered the hit, with his own money, and beat her to the punch, killing her in her home.

Tangential and it bit hard to believe at times, but certainly enough to keep you guessing. From the way he tried to shake Ziva (when he wasn't flirting with her, that is), it felt like something was seriously amiss with that guy. But who knew he would kill to safeguard his laundered money?

Clearly, the rest of the episode took a back seat to Abby's storyline, and Perrette deserves credit for stealing every scene she had in what was a very strong episode overall.

Between this and the two previous installments focusing on Tim and Tony, NCIS has given us some terrific character moments interwoven with the weekly mysteries. So well done.

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

• Could any homicide ever be made to look convincingly like suicide?
• Where was Palmer this week? Wedding planning with Breena?
• Episode head slap count: 1. Season count: 2.
• What's Abby's next move?

What did you think of last night's NCIS? Leave a comment below!

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