While many fans watched the team work to rescue Leon Vance (Rocky Carroll) from terrorist hands, some fans took to social media to express their sadness about missing Abby in the new episodes.
"So happy NCIS is back, but I'll be missing ABBY!!" one user wrote.
"Best TV show on the air. Can't for tonight's episode. Going to be odd without Abby!" another one added.
"It's going to be hard not seeing Abby on my screen every Tuesday night," a third one wrote.
Abby was written out of the series near the end of season 15 after she and Clayton Reeves (Duane Henry) were mugged, which ended with her fighting for her life and Clayton dead.
Clayton's shocking death turned out to be Abby's driving force for the episode, and what led to her leaving the team at the end of the episode.
After the team managed to apprehend the person responsible for the shooting, Abby told her co-workers she was going to take Reeves' body back to London, and intended to stay and help with funeral arrangements before starting a charity organization that Reeves had always wanted to open.
After the heartwarming episode, Perrette released a statement video to fans of the series, thanking them for following Abby since her introduction at the very beginning of the series.
"I hope the fans will remember everything that Abby has taught all of us over the course of this entire run," Perette says in the video. "Just to remember, with me, everything that Abby's given to us. And everything she's taught us. I cannot thank you enough. I am so blessed to have fans like you and it means everything to me."
Former NCIS co-star Michael Weatherly — who now stars in Bull — recently told PEOPLE that he believes Abby will return someday to the series.1comments
"I know that Pauley Perrette will be back in some capacity," the actor stated. "I'm just saying. And I think that she's gonna be — I think everyone misses her already, and she'll be back and funnier than ever. She's a fierce lady and one of my favorite people on the planet."
Hopefully, fans won't have to wait too long for a reunion with Abby in the future. NCIS airs Tuesdays at 8 p.m. ET on CBS.