|Episode Overview||Summary||POI||Cast and Characters||Crew|
|← Season 3 Person of Interest — Season 4 (Flashbacks in parentheses) Season 5 →|
|401 “Panopticon”||409 “The Devil You Know”||417 “Karma” (Finch)|
|402 “Nautilus”||410 “The Cold War” (Greer)||418 “Skip”|
|403 “Wingman”||411 “If-Then-Else” (The Machine)||419 “Search and Destroy”|
|404 “Brotherhood”||412 “Control-Alt-Delete”||420 “Terra Incognita” (Reese)|
|405 “Prophets” (Finch)||413 “M.I.A.”||421 “Asylum”|
|406 “Pretenders”||414 “Guilty”||422 “YHWH”|
|407 “Honor Among Thieves”||415 “Q&A”|
|408 “Point of Origin”||416 “Blunt”|
|“||You don't understand, Mr. Reese. The creator of the game isn't a hacker... it isn't even human. It's Samaritan.||”|
Although Finch insists that he no longer wishes to help with new numbers, his interest is piqued when Reese learns that the newest POI is a brilliant college student engaged in a mysterious, life-and-death scavenger hunt.
Origin of the Title
A nautilus is a type of marine mollusk part of the Nautilidae family of cephalopods, animals with a prominent head and a set of arms or tentacles. A chambered nautilus shell is used to guide players through the game orchestrated by Samaritan.
Main Plot Points
The events in this episode are in Samaritan point of view.
- The Machine continues to send Reese numbers, as he attempts to draw Finch back into the team.
- Finch begins construction in the subway siding.
- Person of Interest: Claire Mahoney, a disaffected college student who hacked into the private network of Silverpool, a Blackwater-type private security firm, in order to discover evidence of a cover-up.
- Reese and Finch soon realize Claire is caught up in game called Nautilus, which she is determined to win, and which requires she follow clues all over New York City.
- Reese begins his new assignment as a homicide detective while he and Finch try to follow Claire.
- Finch slowly realizes that Samaritan is operating the game, possibly to recruit Claire for some purpose.
- Shaw begins working with Romeo. Root cautions her not to be too good a thief so as to avoid attracting attention.
- Samaritan begins to recruit assets from all over the world via the Nautilus game. Its purpose is as yet unknown.
- After reluctantly trying to save Claire from the Nautilus game, Finch realizes he still has a role to play, and rejoins the team.
- The team relocates to a new base of operations, an abandoned subway repair siding.
The New Base of Operations
Main article: The Subway
The team's new base of operations is an abandoned subway repair siding on the Interborough Rapid Transit (IRT), now part of the New York Subway system. Finch is led to the location, which is free of Samaritan's surveillance, by the Machine, which sends messages via spelling errors in Harold Whistler's doctoral dissertation. After outfitting the site with a combination of equipment brought from above ground and materials found in the siding, Finch brings Reese down to see their new headquarters, where they are soon joined by Shaw.
- The Nautilus game is a reference to a real life equivalent, Cicada 3301, which first appeared in January, 2012, then again at the same time in the subsequent years. Believed by some to be an alternate reality game (ARG) or a means to recruit highly intelligent people for some unknown reason, the real purpose of the game is unknown, as is its outcome. It has been attributed to a number of sources, including the National Security Agency or the Central Intelligence Agency, while others believe it may have been created by some sort of secret society.
- Clues in the Nautilus game include a Bongard puzzle, and use of Braille to code the location of the next clue. Braille, a tactile reading system for the blind and visually impaired, consists of six cells in a 3x2 arrangement with one or more cells containing a raised dot. The configuration of raised dots in the cells aligns with the letters of the alphabet and the numerals 0-9. Reading on sight, such as Finch did, would demand a high level of Braille literacy.
- Among the pivotal sites in the Nautilus game is 30 Rockefeller Center, often known as "30 Rock", the headquarters of the National Broadcasting Company (NBC). The building is famous for its ice skating rink and Christmas festivities, the NBC studios tour, and its observation deck, "The Top of the Rock" where Finch and Claire have their final meeting.
- The placement of the nautilus on the banners in the park takes advantage of a visual phenomenon knows as parallax. Parallax is the difference in the relative position of an object from two points of view. In Claire' case, one view of the banners creates the illusion of a series of disjointed white lines near the bottom of the separated banners. However, when she moved, thus shifting her point of view, the banners overlapped, forming a connected image of the nautilus.
- Silverpool is a private military security organization clearly based on Blackwater, a comparable real-world company now known as Academi. Blackwater attracted considerable media attention as a result of its highly visible presence in Iraq resulting from a series of highly lucrative no-bid contracts with the U.S. government, and subsequent questionable activity that resulted in multiple lawsuits.
- Episode co-writer Dan Dietz sketched a concept for one of the pieces of the puzzle.
- The scenes at Toby's Estate Coffee were filmed on July 24, 2014.
- The graffiti mural at the beginning of the episode was painted by New York artist Apache Gonzalez.  The actual location of the mural is W 137th St by 7th Avenue in Harlem, not W 118th and Lenox, as displayed on Finch's phone.
- The biker bar is a real bar in east New York. The patches on the wall which give Claire her next clue were created by prop master Ruth DiPasswuale.
Bloopers and Continuity Errors
- When Finch first enters the GPS coordinates, they pinpoint a spot on 119th St. In the next scene, the same coordinates point to a spot on 118th St.
- When Finch is calling Shaw who just exited OneState Bank, Shaw is wearing gloves holding the phone with her right arm. In the last scene when Shaw is holding a phone, a glove is missing.
- The dog on the lost poster is actually a photo of Producer David Slack's dog. The poster made another appearance in “Q&A”.
- This is the first episode whose ID found in the intro follows a certain pattern: ID.SEE/MMDD.YY, where S is the season, E is the episode number, and M, D, and Y are the month, day, and year, respectively, of the air date.
- This episode may be an homage to Cicada 3301, an online puzzle similar to that of the Nautilus, leading winners to an organization called “Cicada”.
- "You lured me here to assign me your latest number?" (Finch, to Reese)
- "I don't know why a college student needs a firearm, but I think Professor Whistler can figure it out." (Reese, to Finch)
- "You can be a good thief, just not too good." (Root to Shaw)
- "It looks like the game she's playing isn't just real - it's deadly." (Reese, to Finch)
- "Soy milk? I can't stand the stuff. Go cow, or go home." (Shaw, to Barista)
- "How many fingers does it take to make an espresso? You see this okay or do you need me to staple it to your eyeball?" (Shaw, to Barista)
- "I will protect you now." (Samaritan, to Claire Mahoney)