In the third part of the first ever continuous four-episode arc, the truth is revealed. The first part centered on the Gibbs - Abby relationship and the second part on Gibbs' complicated relationship with Ms. Hart. Now the focus shifts again. It's rather neat that each part of the arc examines Gibbs' relationship with a different character. Were this just one loooong plot-arc, it would not stand out, especially as the show is first and foremost about the characters.
The arc plot keeps on twisting and turning. Though Gibbs' loyalties are never in doubt, he is put in a lose - lose situation, which should make most viewers wonder whether the time has come for him to exit the show, one way or other. That. Would. Be. Huge. And should this be the end of Gibbs, Mark Harmon delivers a great performance when, as the pressure increases, Gibbs turns inwards. It is also great that the writers gave Gibbs' opposition not only motivation, but also personality and complex principles.
Season 8 ends on a great sequence of no less than three intercut scenes which leaves the audience waiting for answers to a lot of questions. On top of that, comes the final cliffhanger. As the arc has progressed, the cliffhangers have intensified, and the last one is no exception.
However, when rated as an individual episode, "Rule Fifty-One" doesn't quite equal the best season-enders, which are Season 2's shocking "Twilight" (still the best), Season 5's aptly named "Judgment Day" and Season 6's "Aliyah". It's "only" 8/10, mostly because the plot developments most crucial to the arc are not quite realistic, as has been pointed out in another review. Also, we *still* do not know what really happened in Paris. *That* is just the writers disrespecting the audience. The faithful deserve a reward. Not getting one leaves the audience feeling cheated. Bad writers! Bad writers! They need to be trained.