Person of Interest (2011–2016)
4 user 1 critic

Zero Day 

They wait ten days for a new number due to a system virus, suspecting Root is the problem. It's for Ernest Thornhill, who isn't who, or what, he is supposed to be. At stake is The Machine - will it remain with Finch or end up with Decima?


Jeffrey G. Hunt (as Jeffrey Hunt)


Jonathan Nolan (created by), Amanda Segel | 3 more credits »




Episode cast overview, first billed only:
Jim Caviezel ... John Reese
Taraji P. Henson ... Joss Carter
Kevin Chapman ... Lionel Fusco (credit only)
Michael Emerson ... Harold Finch
Amy Acker ... Root
Brett Cullen ... Nathan Ingram
Jay O. Sanders ... Special Counsel
Carrie Preston ... Grace Hendricks
John Nolan ... John Greer
Al Sapienza ... Detective Raymond Terney
Kevyn Morrow ... IAB Detective Ed Solis
Opal Alladin ... Claudia Sugarman
Sarah Shahi ... Sameen Shaw
Carter Gill ... Office Drone
Mike Masters ... ESU Captain


It's been ten days since the machine has provided a number, which means Carter has had ten days of dead bodies piling up. Finch discovers that a company called Decima is responsible for the virus which is causing these problems of inconsistency. The machine finally does dispense a number, it belonging to Ernest Thornhill, whose business of late has been buying up pay phone companies. As Finch and Reese track Thornhill, who they have yet actually to see, they find out some important information about him and exactly why the machine dispensed his number. But also aware of that fact is Root, who, using her own brand of persuasion, convinces Finch that they need to work together to battle Decima and the virus. Reese becomes aware that Root is back in the picture, he who gets some help from an old acquaintance in tracking Finch and Root. Their competing goals will all come to a head at midnight Eastern time, when the virus is scheduled to do its job. Meanwhile, Carter, in conjunction with ... Written by Huggo

Plot Summary | Plot Synopsis


TV-14 | See all certifications »






Release Date:

2 May 2013 (USA) See more »

Company Credits

Show more on IMDbPro »

Technical Specs


Sound Mix:




Aspect Ratio:

16:9 HD
See full technical specs »

Did You Know?


Harold tells Root that the machine restarts itself "1.618 seconds later". 1.618 is the first four digits of the mathematical Golden Ratio. See more »


Once again, a cellular call between Reese and Carter ends with a dial tone when he hangs up. No dial tone is heard at the end of a call on a cell phone. See more »


John Reese: How did Root get your phone number?
Harold Finch: How does she get anything, Mr. Reese? Subterfuge. She hacks human beings as easily as she hacks computers.
See more »


References North by Northwest (1959) See more »

Frequently Asked Questions

This FAQ is empty. Add the first question.

User Reviews

15 October 2019 | by kasraazizzadehSee all my reviews

This episode is everything you wanted from the season , it had amazing plot twists , revelations and that cliffhanger at the ending just makes this episode one of the best in the whole series

1 of 1 people found this review helpful.  Was this review helpful to you? | Report this
Review this title | See all 4 user reviews »

Contribute to This Page

Women on Set: Celebrating Directors in Their Field

Inspired by The Farewell director Lulu Wang's call to action at the 2020 Independent Spirit Awards, we celebrate women filmmakers working in their field.

Watch the video

Recently Viewed