What happened to Blue in NCIS: Sydney? Spoilers on the dark twist behind her sudden disappearance

NCIS: Sydney season 3 episode 2  aired on October 21, 2025, on CBS. NCIS: Sydney season 3's True Blue episode revealed the Special Agent's backstory to fans and team members after two seasons of anticipation. The third season of the military procedural revealed that Blue had resigned from the team. The shocking decision involved her not meeting with her team again and disappearing after leaving a video message.

The series follows Michelle Mackey's (Olivia Swann) team as they solve complex crimes and reveal dark secrets about themselves. The mysterious character of Bluebird “Blue” Gleeson, played by Mavournee Hazel, has made NCIS: Sydney intriguing. In Season 3, the team's forensic scientist, Blue, was involved in a shocking twist. After a mysterious woman broke into her apartment in Season 2, viewers wondered why Blue disappeared. A terrifying cult backstory was revealed in the answers.

The first episodes of NCIS: Sydney Season 3 hinged on Blue's disappearance. Fans were surprised when Blue left the team due to her past; she tried to escape. In the latest episode, “True Blue,” her sudden disappearance was revealed. The story explores Blue's past and resignation, showing a strong connection to her troubled past.

The Backstory Behind Blue's Disappearance

Upon asking why Blue's backstory was created, in an interview with TV Insider on October 21, 2025, Morgan O’Neill mentioned,

"We spent a lot of time thinking about Blue and crafting her in the first couple of seasons of the show. There’s something tantalizing about someone who knows where all the digital bodies are buried in this world and yet has none herself. We discover little bits and pieces and breadcrumbs about Blue all the way through the first two seasons of the show. We know that she lives on her own."

Morgan also mentioned,

"She has many locks on her doors. She has no digital fingerprint. She asks Doc to look into something for her when they get back from Darwin in a professional capacity. She doesn’t like her photographs being taken."

Blue's story transcends forensics. Sydney, Blue (Faith Mullins), and her twin brother Eli lived in a cult-like commune 17 years before NCIS. The two were raised in a tech-averse community. Rob, their father, tried to escape the commune with them but disappeared.

Blue's absence is discovered when Aspira, a strange woman, visits her apartment in NCIS: Sydney Season 3, Episode 1. Blue returned to the commune after Aspira claimed her twin brother Eli needed her. But when Blue arrived, she saw things differently. She returned for a darker reason than her brother's health.

Aspira brainwashed the commune into believing a prophecy would lead them to the stars by mass suicide.
When Blue investigates, she finds the truth. Aspira planned to trick the group into drinking poison and sell the land for a lot of money. Blue prevented the tragedy, but lost her brother to the poison. Eli survived after being rushed to the hospital.

Blue’s Connection to the Cult and Her Father’s Death

The Blue disappearance investigation revealed a shocking fact about her father's death. A box of human bones was found in Blue's apartment by Evie and DeShawn. A skull from Blue's father, Rob, who left the commune years, earlier was found. Aspira had manipulated Rob, and his body was hidden to hide the cult's dark secrets.

Blue had to face her past after discovering her father's gruesome past and cult membership. She tried to escape her upbringing, but it haunted her as she tried to start over as “Bluebird Gleeson.” Blue's backstory reveals how her experiences shaped her personality and team behavior. The truth about her father's death explains Blue's strange behaviors and protective measures, such as her multiple door locks and reluctance to talk about her past.

Blue's Trauma and Her Potential Return to NCIS: Sydney

Will Blue rejoin the team as the team learns more about her troubled past? Despite her ordeals, Blue is vital to NCIS: Sydney. Her criminal past and revelations complicate her future with the team. Faith Mullins, aka Blue, was convicted of aggravated burglary. After attacking a security guard to steal a portable bone density scanner, she was arrested. Mackey and JD discovered Blue's dark past during the disappearance investigation.

After learning Blue's past, the team must make a tough choice. Blue had fabricated her identity and hidden much of her life from her coworkers. Mackey, who is close to Blue, worries about trust. Blue's backstory and complex character make her an important part of NCIS: Sydney, so she may return despite the fallout. Mavournee Hazel appears in the show's opening credits, indicating her continued journey.

Will Blue return to NCIS: Sydney season 3

The ending of True Blue left fans wondering about Blue's NCIS: Sydney future. After being freed from Aspira and reunited with her brother Eli, Blue's role on the team is unclear. Her criminal record and past secrets have alienated her from the team. The show has not ended Blue's character, so she may return.

Blue's journey is clearly ongoing. She has finally found family and belonging on the NCIS team, a major character development. Blue must rebuild trust with her coworkers after her past revelations. NCIS: Sydney has made it clear that Bluebird Gleeson's story is central to the series, even though her future is unknown.

NCIS: Sydney season 3 is available to stream on Paramount+.