'Zero Day' Ending Explained: Breaking Down Episode 6 of the Netflix Miniseries

The new political thriller Zero Day hit Netflix on February 20, 2025, and the six-episode series details the aftermath and investigation into a deadly cyber-attack that claims over 3,000 lives via a blackout event and threatens to destabilize the entire world. Robert De Niro leads the cast as former President Mullen, a well-liked official who comes out of retirement and back into the spotlight to lead the Zero Day Commission with the help of his confidante Roger Carlson (Jesse Plemons) and his former chief-of-staff with whom he had an affair Valerie Whitesell (Connie Britton).

But as Mullen gets deeper into the investigation, he has to contend with an incendiary right-wing talk show host (Dan Stevens) aiming to discredit him by spreading disinformation, a deeply partisan Congressional body, and a top-secret cyber weapon impacting Mullen’s cognitive abilities. Zero Day is wildly realistic in depicting our current political moment and exposing how vulnerable we are to a potential cyber attack, as much of our technological power is currently being consolidated amongst a few individuals.

So how does Zero Day end and do we find out exactly how—and why—the attack was carried out? Read on for a breakdown of the Zero Day ending.

Who was behind the Zero Day attack?

It’s revealed that Monica Kidder (Gaby Hoffmann), a tech billionaire with her own financial interests, played a large role in releasing the malicious code onto people’s phones, as her company owned 80 percent of the apps on people’s devices. But she didn’t act alone. Kidder had insider help, namely from Speaker of the House Richard Dreyer (Matthew Modine) and former President Mullen’s daughter, Congresswoman Alexandra Mullen (Lizzy Caplan), among other government officials across both sides of the aisle. They also received financial backing from billionaire Robert Lyndon (Clark Gregg).

Why did they execute Zero Day?

The series hits close to home when describing the partisan and divided environment we live in, as Speaker Dreyer explains that the group intended to utilize the attack as a way “to cut off the political fringe on both sides, to expose a vulnerability that has been mistaken for freedom, and to restore a shaken faith in the ability to govern.”

Executive producer, co-creator, and co-showrunner Eric Newman has expounded upon that, telling Netflix’s Tudum, “They weren’t looking for money, they weren’t looking for revenge; they were looking to make the world a better place. And a lot of the worst endeavors in human history begin that way.”

Of course, too much power can lead to corruption, and former President George Mullen rightfully warned that concentrating power and manipulating systems are the work of dictators, not democracies.

Is the truth revealed to the American public in 'Zero Day?'

Yes. During the live broadcast of President Mullen’s congressional address, he abandons his prepared remarks that would have pinned the entire catastrophe on Kidder. Instead, he reads a letter from his daughter Alexandra indicating her intention to turn herself in before outing the other parties involved. Mayhem begins to break loose in the room but by the end of his speech, Mullen receives a significant round of applause for exposing the crimes committed within their own walls. Newman told Tudum, “There are going to be a lot of questions about whether this is a happy ending.”

Before the speech, the sitting president, President Mitchell (Angela Bassett), asks President Mullen to keep the exact findings under wraps to protect her future reelection aspirations, claiming that the country can’t handle the truth. However, the last time we see her, she has a sly smile on her face—perhaps indicating that she knows she can claim this win as her own.

Does anyone die in the 'Zero Day' finale?

Kidder is killed in the penultimate episode, and there is a vicious mob that attacks President Mullen right after a second blackout event, but both he and his wife Sheila (Joan Allen) make it out alive. Mullen’s team does use the chaos of the protesters to fake his death momentarily to gain access to the group behind the attack, but there aren’t any further casualties in the finale.

What is the future of Valerie and George's relationship in 'Zero Day?'

One thing that is not revealed to the public is that Valerie’s 12-year-old daughter Lily (Charlotte Ewing) is the product of her affair with President Mullen while he was in office. Lily and George don’t know about each other until the end of the series, and Valerie gives Lily the choice to pursue a relationship with her biological father.

It’s unclear whether Sheila knows that Lily is her husband’s daughter, but Joan Allen’s performance exudes a certain air of poise and knowingness, indicating this probably isn’t news to her.

Is George Mullen cured of Proteus in 'Zero Day?'

Proteus—the top-secret technological weapon that severely impedes memory and invokes hallucinations—was administered on Mullen, and he doesn’t seem to recover from the attack. It manifests in a fixation on the Sex Pistols song “Who Killed Bambi” throughout the series and Mullen sees the words on the teleprompter during his speech to Congress; later he has visions of his late son.

Mullen finds a mysterious object in a bird feeder on his property that he assumes is connected to Proteus, but the tests come back inconclusive; this ambiguity was intentional. “When Noah [Oppenheim] and I designed the season and wrote the show, we made a pact with each other that Proteus was being used, but that it should be open to interpretation,” Newman told Tudum. “Our personal belief when we were writing the show was, yes, Proteus was being used on Mullen. Having now watched the show, I’m not so sure.”

By the end of the finale, Mullen seems to have kept the symptoms mostly at bay as he returns to his quiet private life. The final sequence reveals President Mullen burning the pages of his memoir manuscript—his legacy has been irrevocably altered for better or worse—before heading out for a walk with his dog.