"Didn’t realize how much" — Lizzy Caplan from Netflix's Zero Day breaks down her character's involvement in the twist ending

Zero Day on Netflix, starring Robert De Niro, took the audience by surprise with its twisted finale. In the thriller series, De Niro is cast as former President George Mullen while Lizzy Caplan plays the role of Alexandra Mullen, George’s estranged daughter and a congresswoman. The story follows George Mullen as he investigates a devastating cyber attack that creates panic through the country and results in casualties.

The article contains spoilers about the series. Reader discretion is advised.

In the finale, it is revealed that Alexandra is one of the names behind the attack. Caplan was surprised by the intensity of her own character. She said:

‘I think it was probably before I read the scripts. I may not have been as aware of the magnitude of her role in it. Maybe I thought there were going to be other people who were involved, but I didn’t realize how much of it was going to be Alex.’

Zero Day premiered on Netflix on February 20, 2025. The series has a star-studded cast including Robert De Niro, Angela Bassett, Lizzy Caplan and Jesse Plemons, among others. Created by Eric Newman, Noah Oppenheim and Michael Schmidt, Zero Day comprises six episodes. The director of the series is Lesli Linka Glatter. The storyline explores the American political landscape while dealing with betrayal, morality and strained family dynamics.

---

What is Zero Day about?

Robert De Niro plays former President George Mullen, returns to the political scene to investigate a damaging cyberattack. While they initially believe that Russia is behind the attack, investigations soon reveal that the attack is orchestrated by forces within the US government. Struggling with personal issues, and tackling political hurdles and corruption, Mullen must uncover the truth before it is too late. Mullen’s daughter and congresswoman Alexandra Mullen emerges as a key player in the conspiracy.

---

Alexandra Mullen in Zero Day finale

In the finale, Alexandra confesses to her father about how she was instrumental in setting off the cyber attack. She reveals that she became a part of the plot along with the speaker of the house, Richard Dreyer (played by Matthew Modine), and tech billionaire Monica Kidder (Gaby Hoffmann), as a move against the current government under President Evelyn Mitchell (Angela Bassett). At the end of the show, Alexandra’s fate is unknown as George goes on live TV and exposes the culprits behind the conspiracy including his own daughter.

Speaking to Variety, Caplan said about Zero Day:

‘The political aspects obviously are driving this story forward, and this is what the show is about: What would happen if something this awful happened to a country that’s this divided where we didn’t really know who to trust and we didn’t know who was telling the truth? And [what] if the truth became more subjective instead of what it’s always been? I found it all very compelling.’

She spoke about the confrontation in the finale:

‘….I do think many people can relate to the idea that you think you know better than your parents, that your parents are drawing from an old playbook and they don’t get how things really work now in the modern age. That is Alex’s fatal flaw.’

Zero Day is a thriller series currently streaming on Netflix.

Read More: Zero Day Season 1 Recap and ending explained: Why did Richard Dryer want the Zero Day Commission?

---

For more interesting stories, stay tuned to SoapCentral.