The Ending Of NCIS Season 21 Explained: How The Finale Sets Up Season 22

Contains spoilers for the Season 21 finale of "NCIS"

"NCIS" fans have definitely been left hanging by the Season 21 finale, and not just because we've discovered a whole lot more of Alden Parker's (Gary Cole) previously obscured backstory. 

The biggest twist is Jessica Knight (Katrina Law) getting a job advancement offer from Leon Vance (Rocky Carroll). He asks heR to be the chief REACT training officer at Camp Pendleton, which would require her moving. The job once belonged to her father, but to take it, she would need to leave not only the NCIS world behind, but her blooming relationship with Jimmy Palmer (Brian Dietzen). She applied for it three years before, well before their relationship began, so she's in a bit of a pickle. Knight has a day to decide what she's going to do — an extremely eventful one, it turns out, when what was supposed to be a simple boat decommissioning reveals a crime scene when three dead bodies turn up inside the vessel. Her day gets worse when Jimmy dumps her after learning about the REACT position.

Knight and Parker investigate, but it turns out their Does all died in different ways and are socially unconnected. They find themselves trapped on the ship by the perp, and Parker is injured. While he's bleeding out, we learn more about his tragic backstory – including a closed-off navy man father and troubled relationship with his mother — and he sees a hallucination of a little girl in white he calls Lily. The team rescues Jessica and Parker, and at the hospital Jimmy and Jessica make up. But when Vance asks Jessica for her decision? She's all on board with the job switch.

That leaves us with two big cliffhangers — who is this mysterious Lily Parker knew as a youth? And will Jessica really go to Camp Pendleton?

Will Jessica switch coasts? Will we ever find out more about Aiden's childhood? While fans are probably scared Knight is on her way out, that plot twist remains to be confirmed. Katrina Law told Deadline in May that "Reef Madness" fittingly signals a sea change in the show's make up. "Some big fundamental changes are about to happen," she said.

"There are a lot of things that are going to be happening, not just the danger that our characters are put through, but also dynamics that are going to be shifting. Potentially even between Jimmy and Jess, this couple that has been fantastic for the last two years," Brian Dietzen said at the same event. 

Dynamics are already changing among the crew, but viewers are going to have to wait a little while to find out how Jessica's job switch goes — and how long it lasts. "NCIS" won't return to its traditional Monday night perch until September.