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301Liberty309The Crossing317Root Path (/)
302Nothing to Hide310The Devil's Share” (Multiple) 318Allegiance
303Lady Killer311Lethe” (Finch) 319Most Likely To...
304Reasonable Doubt312Aletheia” (Finch) 320Death Benefit
305Razgovor” (Shaw) 3134C321Beta” (Grace)
306Mors Praematura314Provenance322A House Divided” (Collier)
307The Perfect Mark315Last Call323Deus Ex Machina” (Collier)
308Endgame” (Carter) 316RAM

POI 0311 Main



Air dateDecember 17, 2013

Running time

Production code2J7611

Written byErik Mountain

Directed byRichard J. Lewis


Images (52)

There was a second machine, and Arthur built it.

— Finch

"Lethe" is the 11th episode of season 3, and the 56th produced hour of Person of Interest. It originally aired on December 17, 2013.


Flashbacks to Finch’s adolescence provide insight into his creation of the Machine. The team receives the number of a man dying of a brain tumor as Reese leaves the POI team behind in the aftermath of the war with the crime organization, HR.

Origin of the Title

Lethe (Λήθη) in Greek mythology is the river of forgetfulness. It is one of the five rivers flowing into the Hades, the Underworld; drinking its waters causes the drinker to forget. It is also the name of the goddess of forgetfulness. 

Main Plot Points


Episode Notes

  • Sodium Pentothal is a barbiturate used for anesthesia, and in small doses, as a "truth serum". It is identifiable by its strong odor of garlic and onions, which Shaw detected when she sniffed the syringe.
  • According to the PET computer, the episode takes place on Dec 17, 2013, the original airdate of the episode.
  • Root received the number instead of Finch, this indicates that Root has a way to communicate with the machine without the use of a telephone.
  • When the Machine begins calculating the possibility of Samaritan's reactivation, it also brings up evaluations of other real intelligence programs, including Able Danger, Genoa, Genoa II, Fairveiw, Bullrun, and PRISM. The first three are listed as "deactivated" while the latter are described as "active decoys" to Northern Lights.
  • This episode is the first part of a two episode mini-arc; the POI and storyline of this episode carry over into the next episode, “Aletheia”.
  • This episode is the beginning of the Samaritan arc, an arc that continues to the series finalie “return 0”.

Production Notes

  • POI 0311 Control1
    This episode includes the first appearance of Control. The alert viewer might have seen a red box appear around her when she exits the elevator during their escape the hospital. She only appears on screen for half a second.

Bloopers and Continuity Errors

  • The number that Root gives Finch (229-00-8003) is different than the number on Arthur's medical records (XXX-XX-9019). The former one was also Nicholas Donnelly's number in “Prisoner's Dilemma



  • The bartender at the Roadhouse is the actual bartender and not an actor.[1]
  • When the Machine tries to predict the outcome of the situation at the end of the episode, it says that the names: Sameen Shaw and Robert N. Hersh are aliases.
  • Also when predicting outcomes, in the lower right corner on the screen we can see that the Machine is "Retasking Analog Interface", which is Root.
  • Again in the Machine's predictions, when it calculates the probability of operational conflicts with Samaritan, we can see for less than a second that there is a 37.16% probability of a Russian Revolution and that the nuclear proliferation in Iran is at 25.28%.


  • "Not sure I like being associated with your former employers, who tried to kill you." (Finch, to Shaw)
  • "Should I be looking for some action elsewhere?" (Shaw, to Finch)
  • "If they don't want you to get inside, they ought to build it better." (Young Finch)
  • "He is not deceived, who knows himself to be deceived." (Arthur)
  • "If I keep working on it, I think I can make it so it can remember all the things you can" (Young Finch, to Finch's father) "Now, we talked about this. I mean, what's wrong with me can't be fixed by you, or anyone else, okay?" (Finch's father, to Young Finch)
  • "But what if I build a machine with lots of memory, one that could think?" (Young Finch) "Even if you could... even if you could fill it with all my memories, it still wouldn't be me. Not everything that's broken is meant to be fixed, understand?" (Finch's father)
  • "Dude, that was too much fun to be legal." (Finch's friend)
  • "It just proves that no matter what we do or don't do in this world, bad things are going to happen. It's pointless. Irrelevant." (Reese)
  • "The truth fears no questions." (Arthur)
  • "One of you is going to tell me what it is I want to know. And whoever does, will be the one who gets to leave here... alive." (Control)
  • "The kind you need a gun for." (Shaw, regarding what kind of people were pursuing Arthur)
  • "Talking is overrated... I mean, that must have been really hard." (Shaw, to Arthur's wife)
  • "What do you think, I won my detective shield in a poker game?" (Fusco, to Reese)



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