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Episode Overview   Summary   POI   Cast and Characters   Crew    
  Person of InterestSeason 1 (Flashbacks in parentheses) Season 2 →
101Pilot” (Reese) 109Get Carter” (Carter) 117Baby Blue
102Ghosts” (Finch) 110Number Crunch 118Identity Crisis
103Mission Creep” (Reese) 111Super” (Finch) 119Flesh and Blood” (Elias)
104Cura Te Ipsum 112Legacy 120Matsya Nyaya” (Reese)
105Judgment 113Root Cause 121Many Happy Returns” (Reese)
106The Fix 114Wolf and Cub 122No Good Deed” (Finch/Ingram)
107Witness 115Blue Code” (Reese) 123Firewall
108Foe” (Reese) 116Risk
Root Cause

1x13 RootCause



Air dateFebruary 2, 2012

Running time43:57

Production code2J6213

Written byErik Mountain

Directed byRichard J. Lewis


Images (27)

You can call me Root.

— Root

"Root Cause" is the 13th episode in season 1, and the 13th produced hour of Person of Interest. It originally aired on February 2, 2012.


Reese and Finch's latest POI is a down-on-his-luck man who may have reached his breaking point. As the case evolves, the duo calls upon a former POI for help, the resourceful and well-connected Zoe Morgan.

Origin of the Title[]

Root cause generally refers to the thing primarily responsible. Here it is a play on words because the perpetrator is named Root.

The term "Root" also comes from the word "Rooting" in programming. Rooting is the process of allowing users of smartphones, tablets and other devices running the Android mobile operating system to attain privileged control (known as root access) over various Android subsystems – which Root is doing by taking the control over Finch's system through hacking.

Main Plot Points[]

  • Person of Interest: Scott Powell - an unemployed man who got framed for a murder of a Congressman Michael Delancy.
  • Reese has to abduct the POI after he is framed for murder, because the killers intend to kill the patsy.
  • Zoe Morgan makes a reappearance and provides evidence of the real killer. Reese learns more about her background and an intimate relationship is suggested.
  • Root and FBI agent Nicholas Donnelly are introduced.

Episode Notes[]

  • First appearance of Root who will later become a main character and an integral part of the team.

Acronyms and Vocabulary[]

  • Honeypot: A small network that is setup to create the appearance of major network. Architects of this type of network hope that a hacker might be enticed by the falsely generated "network traffic" long enough to trace the intruder's whereabouts. Its name derives from the notion of flies being drawn to honey.
  • Worm: Malware, or a potentially unwanted program, that replicates without the aid of being attached to another program. Its purpose can be anything from slowing down network traffic, consuming CPU time, disk space and  memory, to stealing (or destroying) data.

Production Notes[]

  • The IP address (452.34.256.193) used to communicate with Root is not possible and IRC is typically on port 6667, not 96. These may be intentional. Using IP addresses and IRC ports that don't exist prevents potential problems and abuse that could arise from viewers inadvertently using legitimate IP addresses and IRC ports, much like how virtually every phone number used in TV and films has a "555" prefix, which is not used for any real phone numbers.

Bloopers and Continuity Errors[]

  • At the end of the episode when Root contacts Finch, her final text before disconnecting is merely "...Harold"; however, in the previous shot as she is shown typing this word, the keys she presses are completely unrelated. She starts by keying b, then s, then 3.
  • Matheson's gun is in his right hand after his "suicide" yet there's no wound on the right side of his head which is facing up, indicating he shot himself on the left side of his head with his left hand.


  • Reese and Scott Powell take a 1 train to Grand Central Station, and the hitman following them gets off an A train. In real life, neither 1 nor A trains go to Grand Central Station. The platform where they get off the train and call Scott's wife is used by an S train (shuttle) that stops only at Times Square and Grand Central. They wouldn’t use it for a getaway since it goes nowhere. From a production standpoint though, it’s the easiest train to shut down for filming.
  • In the subway station, Reese leads the hitman into a bathroom. In real life, no bathroom exists in that corridor. The door Reese opens really leads to a storage room, and then the camera cuts to a bathroom in a studio.
  • Powell's car has the same license plate (EWQ-2147) as Fusco's car in “Ghosts”.
  • The roles of the Asian policeman coming into Matheson's home and the Asian journalist asking Scott Powell questions in front of his yard at the end of the episode were played by the same actor.
  • The method of attack Root uses against Finch is called a Distributed Denial-of-service (DDoS) attack. The way it works is several systems or bots flood the bandwidth or resources of a targeted system. The key advantage of a DDoS attack is that it uses several systems attacking at the same time, which makes it harder to counteract. While the Machine classifies the attack as Distributed, it is somewhat more similar to a Permanent Denial-of-service (PDoS) attack. In this attack, the targeted system is so badly damaged that it requires replacement or re-installation of hardware. PDoS attacks exploit flaws in networked systems which can allow remote access from one device to another. PDoS attacks are also faster and require less resources than DDoS attacks.


  • Ramin Djawadi created a musical theme for Root which is a Twilight Zone type repetition of sinister notes. These are mostly playing softly in the background, but then become loud when Finch taps into the honey pot. This piece of music is the only reason Amy Acker and the character of Root survived from this episode to become a main part of the cast per Jonah Nolan.[1]


  • "If there is one thing our little venture has proven, Mr. Reese, it's that people are rarely what they seem" (Finch)
  • "There are no bathrooms on a stake out, Finch" (Reese)
  • "I haven't been able to unmask the hacker's IP, but here's a vulnerability in the firewall. Yes! Okay... now we're in. So now let's see who's behind the curtain."  (Finch)
  • "Wait, something's wrong. We didn't hack in, we were let in. It's a honeypot! Incredibly sophisticated... they're using a worm to infect any devices connected to our private network, including our phones. They're listening to us right now, destroy your phone. You know how to find me." (Finch)