The curtain fell on this season with the NCIS Season 18 finale "Rule 91." So, beware of spoilers below as we delve into last night's episode and news about the upcoming season.

Much of the talk about NCIS Season 19 has focused on the "to do or not to do" issue of Mark Harmon's demotion. However, even the "NCIS" Season 18 finale seemed to leave a great deal of potential for the future, with no unilateral commitments.

But more on that later, starting with a focus on the characters who left the series in the "NCIS" Season 18 finale and why it is by no means unlikely that they are gone for good. Yes, the trailer for "Rule 91" didn't fool us: Eleanor Bishop (Emily Wickersham) left the series after eight seasons on it. [The leaked NSA documents were a cover for her leaving the NCIS team in a convincing way. Now Bishop is headed for an undercover opportunity, and Odette (Elaine Taylor) has helped trap her in order to convince her.

The only member of the NCIS team who knows about the plan is Torres (Wilmer Valderrama), with whom Bishop locks lips in a touching scene. It turns out that the two are not actually together yet. And since Torres knows the truth (and demands answers), there is a great emotional atmosphere here that suggests the possibility that Bishop will one day return for him.

Nevertheless, Bishop got some other features of the farewell episode. McGee's conversation with Gibbs suggested the possibility that Bishop's run might actually be over. The earliest she could return would be the season 19 finale.

Nevertheless, Gibbs' season also came to an explosive conclusion. After discovering that his and Marcy's home was being bugged by a serial killer, Gibbs piloted the "Rule 91" (his ship's name meaning "good-bye") to follow the clues.

The Rule 91 then said "good-bye" and was blown to pieces. First, Gibbs' body floated to the surface, making us think he was dead, and then he swam away without being seen.

Of course, Gibbs' survival makes all the sense, as we know that Harmon will return. But was this sequence of events meant to serve more than one master?

If Harmon had not re-engaged, the scene might have ended with Gibbs' corpse floating on the surface of the water. Also, since Gibbs swam away, could he be spending NCIS Season 19 in hiding and trying to root out the culprits who bugged his home?

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