Zero Day ending explained: What happens to Mullen?

Zero Day is a political thriller produced by Eric Newman, Michael Schmidt, and Noah Oppenheim for Netflix. The limited series, helmed by Lesli Linka Glatter, made its premiere on February 20, 2025.

This political conspiracy thriller centers on a horrific hack that paralyzes the United States and kills thousands of people. George Mullen, a popular and well-respected former US president who battles his personal problems and leads the investigation into a statewide cybercrime, is the focus of the exciting and horrifying limited series.

Disclaimer: The article contains spoilers for Zero Day.

As Mullen gets close to uncovering the perpetrators of the cyberattack, his life is threatened by those in the government. However, despite the pressure from the President to bury the truth, he publicly announces the true findings of the investigation.

The show features an ensemble cast including Robert De Niro, Lizzy Caplan, Jesse Plemons, Joan Allen, Connie Britton, Bill Camp, and Angela Bassett.

Geroge Mullen is tasked to lead the Zero Day Commission

The series begins with an insight into the mundane daily life of George Mullen, a former President of the United States who is not retired from public life. He swims, hikes with his dog, and is behind the deadline for his memoir.

Suddenly, a cyberattack that downed all the communication and transportation networks for a minute transforms an ordinary day in the lives of Americans into a post-apocalyptic nightmare. The government, led by President Evelyn Mitchell, asks Mullen to visit the affected sites and encourage people to stay patient and brave.

Mitchell later announces that the government is forming a commission called Zero Day Commission to investigate the deadly attack. This commission has the power to temporarily engage in extra-judicial activities such as mass surveillance, making arrests, and detaining suspects without warrants. It is led by George Mullen, who reluctantly accepted the offer.

Mullen battles his personal demons during the investigation

As Mullen leads the most important investigation in modern American history, his health becomes a matter of concern for his wife and colleagues. He begins to hear the 1980s rock song Who Killed Bambi and hallucinates about seeing Anna Sindler, a literary agent who died in the Zero Day attack right after meeting Mullen for his memoir.

Mullen is also grilled in media by a provocative podcaster, Evan Green, whom he gets arrested without a warrant and enables enhanced interrogation techniques to find a link between him and the attackers. However, his actions might have resulted from a desire for a personal vendetta.

Mullen has to deal with several personal problems during the intense investigation. He faces constant pressure from his daughter, Congresswoman Alexandra Mullen, to quit leading the commission. Additionally, his wife, Sheila Mullen, suspects that he might not be mentally sound enough to continue the investigation.

However, the two biggest demons that Mullen fights are the trauma of losing his young son to a drug overdose and the potential presence of a neurological weapon, Proteus, which may or may not be the cause of his hallucinations. It is later revealed that the song Who Killed Bambi was playing on the music player when he found his son dead.

So, the reason behind his hallucinations might be a trauma response and mental deterioration due to old age and not the use of Proteus on him. However, the show never conclusively provides an answer. But despite dealing with personal, political, and media issues, Mullen finds the people behind the Zero Day attack.

Also read: Zero Day: Everything to know about the Netflix thriller starring Angela Bassett

Mullen announced the true findings of the investigation in front of the world

Mullen's close confidante, Roger, left a note in his diary that assisted in revealing the secret behind the Zero Day attack. The note said that the attack was not the work of any random domestic terror organization but a comprehensive political plot by powerful businessmen and government officials to seize power. It was also revealed that his daughter Alex was also a participant in this horrible crime that claimed over 3400 lives.

On the other hand, the reason why President Mitchell asked Mullen to head the commission was that she already suspected the involvement of her own government officials in the Zero Day attack. However, when the scale of internal involvement came out, she asked him to bury the truth and not name the people within the government in his upcoming report.

While the world was watching, Mullen read a sanitized version of the Zero Day Commission report. However, he soon changed his mind, read Alex's written confession, and named all the real conspirators. With that, he concluded the work he was assigned with dignity and honesty.

Also read: 7 shows to watch if you like Zero Day season 1

Interested viewers can stream Zero Day on Netflix.

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