‘NCIS’: Who Tried to Kill [Spoiler] in the Season 18 Finale?

NCIS Season 18 Team Bishop Gibbs McGee Torres
Spoiler Alert
Sonja Flemming/CBS

[Warning: The below contains MAJOR spoilers for the NCIS Season 18 finale “Rule 91.”]

One of the major questions as NCIS neared the end of its 18th season was simple: What is Leroy Jethro Gibbs’ (Mark Harmon) future with the show? The finale may have hinted at what’s to come.

Amidst rumors that Harmon could be only around part-time in Season 19 — which started back before the series was renewed — the final scene of “Rule 91” may have set him up for just that. Since his suspension (he beat up a man who was killing dogs and expressed zero remorse), Gibbs has struck up a friendship and partnership with investigative reporter Marcie Warren (Pam Dawber). Together, they’ve been looking into a serial killer responsible for her friend’s death.

In the finale, Marcie seemed to have discovered the killer’s pattern and determined there was a victim they’d missed. Despite Gibbs telling her he’d been followed and finding bugs in his basement and her office, Marcie insisted on continuing to pursue her investigation. Separately, both found the boat likely used to dump the fourth victim’s body, and thanks to pine cones Gibbs found, had an idea where that was. That’s when Gibbs refused to let Marcie go any further.

And in the final scene, he was on the water, in his boat (named Rule 91 — “when you decide to walk away, don’t look back”), happy, smiling… when it exploded (the back, first). Gibbs was floating, leaving us to wonder if NCIS wanted fans to think he could be dead all summer, before he began swimming away.

However, we are left with the question of who put the bomb in his boat. We have a few theories.

NCIS Bugs Gibbs Marcie Office Season 18 Finale

Cliff Lipson/CBS

The Serial Killer

It’s simple: Gibbs and Marcie have gotten too close, and the serial killer decided to (try to) take them out. Someone was following Gibbs and did bug his basement, where he was building the boat, after all. And Gibbs did stop at a gas station. Maybe the serial killer was following him (again) and took advantage of an opportunity. But that seems too obvious and there are a few problems with that logic (keep reading).

An Enemy From Gibbs’ Past

Though some of the same problems arise with anyone being behind the bomb, we can’t rule out that one of Gibbs’ many enemies could have used any opportunity to go after him. With another season coming — and with NCIS closer to the end than the beginning — why not explore another part of his past?

A New Threat

Right now, Gibbs is indefinitely suspended from NCIS. Bishop (Emily Wickersham) may have questioned if he’s ever going to return in the finale, but maybe this is the beginning of his way back to the agency. Maybe the bombing is unrelated to anything from his past or present. Maybe it’s a new threat that will require him to return to his old workplace and team.

NCIS Rule 91 Gibbs Boat Season 18 Finale

Cliff Lipson/CBS

Gibbs Himself

Honestly, we may be leaning towards this one. Gibbs knew he was being followed. He was moving around his tools in his house when McGee (Sean Murray) stopped by and was vague about what he was doing. The bomb seemed to be placed just right to destroy the boat but not kill Gibbs. Who would know better where to put it than Gibbs himself?

Gibbs knew he was being followed and he found a bug in his basement. Would he really not check the boat to make sure there was nothing inside it or then leave it unattended and not check it before going out in it? He may have been suspended, but he’s still a seasoned agent.

We have a feeling this is part of Gibbs’ plan to track down that serial killer himself and can be used to explain any absences from Harmon, depending on how much of Season 19 he’s in.

Plus, he named the boat “Rule 91.” Doesn’t blowing it up suggest that he’s not walking away?

NCIS, Season 19, Fall 2021, CBS