Warning: Spoiler alert! Do not proceed if you have not watched Tuesday's finale of "NCIS."
"NCIS" said an emotional goodbye to Pauley Perrette.
On Tuesday's episode, titled "Two Steps Back," Perrette's Abby Sciuto bid adieu after 15 seasons on CBS' veteran procedural -- and she received a memorable send-off. After nearly dying following a targeted attack that mistakenly claimed the life of fellow NCIS team member Clayton Reeves (Duane Henry), Abby vowed to ensure that Reeves' sacrificing his life for hers wasn't done for naught.
After gathering members of the NCIS team -- minus Gibbs -- around for her "big announcement," Abby revealed that she was going to make sure Reeves' wish for his final resting place to be beside his late mother is met.
"Reeves wanted to be buried next to his mother in London, so I'm going to escort his body there tomorrow and make the arrangements," she begins. But when she's asked if she's "coming back," Abby tries to communicate to the group that this will be a permanent change.
"I'm not coming back," Abby says again. "I'm leaving NCIS."
The announcement of her departure takes everyone by surprise; after all, Abby is NCIS.
"Clay died saving my life and I owe him a debt and I intend to see it through," Abby says, laying out her post-NCIS plans. "Clay always wanted to start a charity in honor of his mom. Since he's not here to make that happen, I will. You may not understand, but it's something that I have to do, not just for him but for me."
"It wasn't an easy decision," she continues. "You guys are my family and this is my home, but you have to go with your gut and my gut is telling me that I have to go."
Abby shares a moment with each member of the team, but it's a particularly emotional one with McGee that seems to suggest that there's room for Abby to return at some point down the line. "It's not goodbye for good, it's goodbye for now," she assures McGee and viewers.
Later, Abby leaves a letter on the front door of Gibbs' home, expressing her thoughts on how much he's meant to her all these years.
"Hey Gibbs, you're probably wondering what's with the retro communication. Truth is, I chickened out. I was afraid if you asked me to stay, I might waver," she writes. "There's nothing I wouldn't do for you. When I think back on when things in my life got difficult, you were always there to tell me that it would be OK. And it would be because you would make it OK. But Gibbs, Reeves is gone and it's not something anyone can fix. Not even you."
"I hope you know what you mean to me. Every moment. Every lesson. Every hug. I'm thankful for it all, no matter what we faced over the years. There was always ever only one thing I ever needed to hear from you," Abby's letter concludes, before a flashback to an early conversation she shared with Gibbs plays over.
Abby: "Tell me that I made a mistake."
Gibbs: "No, I can't say that."
Abby: "Tell me how much I've been like a daughter to you and how much you love me."
Gibbs: "Will that help?"
Abby: "No. What I really need to know is, Gibbs, is you're going to love me no matter what."
Gibbs peers out of his window and sees Abby standing across the street, waiting for a response. Finally, Gibbs gives Abby the answer she's been looking for.
Earlier in the evening, former "NCIS" star Michael Weatherly, who left the series in 2016, shared a heartfelt message to Perrette ahead of her final episode. "Pauley Perrette, series finale. I'll be watching with a box of Kleenex," Weatherly said in a video he captioned, "I will be watching #abby tonight on #ncis and telling my kids,'...it's ok. It's ok.' Big kiss!"
Last week, Perrette spoke with ET's Kevin Frazier about saying goodbye after 15 seasons.
"I just made a very feeble attempt to try and tell them without crying and I made it for about 10 seconds," she said of breaking the news that she was leaving the series to her "NCIS" cast and crew. "'I just want you guys to know...' and that was it. I'm like, [crying], 'I love you, guys,' then I have to get right back to work and do a three-page monologue about science."
"NCIS" airs Tuesdays at 8 p.m. ET/PT on CBS.