John Reese is the name adopted by the former U.S. Army Special Forces soldier and Central Intelligence Agency (CIA) officer who serves as Finch's armed enforcer to stop future crimes.
Harold Finch is a reclusive billionaire software engineer who built a machine that predicts future crimes and outputs either the victim's or perpetrator's Social Security number.
In her first appearance, she claims that she has an Axis II (psychology)Personality disorder and alexithymia, making her unable to feel and/or express common human emotions like fear or sadness.
Aside from her extraordinary intelligence, she has also displayed an uncanny ability in the use of firearms, a very high threshold for pain (S2 Ep2, "Bad Code", where she gets physically assaulted by Denton Weeks; S3 Ep12, "Aletheia", where she is severely tortured but not broken by Control) and a proficiency for social engineering.
Root cleared out of her location, the dorm room of an uninvolved college student away on winter break, before the FBI, acting on an "anonymous" tip (from Finch) could apprehend her.
Carter crossed paths with homeless John Reese ("Pilot") following his encounter with a group of young men on a New York City subway, but she later reconnects with him as the mysterious "Man in the Suit".
This incident, and the death of two of her fellow detectives – Bill Szymanski and Cal Beecher – motivate her to go against HR and arrest its mastermind, Alonzo Quinn, without resorting to the vigilante justice of Reese and Finch.
("return 0") Nathan C. Ingram (played by Brett Cullen) is Harold Finch's deceased collaborator and business partner who co-created the Machine, and died under circumstances not known until "God Mode".
On September 11, Ingram visits Finch while he is working on a new program, in order to break the tragic news of the terrorist attack on the World Trade Center earlier that day.
On June 10, 2002, following another ceremony, and after dismissing half of his company's staff, Ingram arrived at an abandoned office floor in the building, and discovered Finch's progress with the Machine.
Using her own sources, independent of Reese and Finch, Zoe figured out that the woman in the recording was Dana Miller, a former employee of Virtanen, who was going to blow the whistle about one of their drugs and was killed for her trouble.
Harper Rose (played by Annie Ilonzeh) a drifter and opportunistic con artist who first appears as a person of interest when she tries to independently double-cross both a drug cartel and The Brotherhood.
In Logan's case, along with getting Reese into the function, he knocked out power to the house being used as the terrorists' base of operations, allowing Shaw and Fusco to take them down and anonymously alerted the Secret Service to the threat.
(5.1 "BSOD") Soriano is part of a joint investigation with FBI Special Agent Martin LeRoux that is looking into Fusco's version of the circumstances of the deaths of Dominic and Carl Elias.
The following characters are involved in the HR storyline, in which a group of corrupt police officers work in collaboration with an up-and-coming mob boss to control organized crime in New York.
Alonzo D. Quinn (played by Clarke Peters) is a political adviser for New York City councilman and mayoral candidate Ed Griffin (Richard V. Licata) and the leader of HR.
Quinn however leads his candidate Ed Griffin to an even greater victory by framing Landon Walker as the leader of HR and restoring Angelis' career in the process ("Bury the Lede").
("The Devil's Share") New York City Police Department Captain Arthur 'Artie' Lynch (played by Michael Mulheren) was a major figure in HR with whom Fusco must appear to be working.
Despite first appearing in the background ("Cura Te Ipsum"), he did something of a more credited role in which he invited CIA agent Mark Snow, Tyrell Evans and Carter into his office to talk about Reese ("Number Crunch").
After Ingram died, Corwin quit her job at the government and moved to Green Bank, a small town in West Virginia that does not have cell phones or wireless internet ("Wolf and Cub").
Prior to that promotion, he had already been working in corporate law for a decade as a member of the White House legal team and a specialist in security policy ("Bad Code").
After a bomb in the post office goes off and Vigilance is falsely implicated, Garrison readily agrees to Greer's demands for complete control and he allows Samaritan to go online.
Parallel to corrupting the Corwin investigation, Special Counsel also sent Hersh to track down Denton Weeks, who had disappeared on private business and was later found dead after Root shot him ("Bad Code").
When a Samaritan representative refuses to allow Control to review the contents of a relevant threat's laptop, she secretly enlists Grice's help to continue the investigation.
Alongside Alicia Corwin, they gave orders to Reese and Stanton to go to Ordos to retrieve a laptop containing information pertaining to a computer virus that could disable nuclear programs.
Later, he received information that Reese had escaped to northern Connecticut where his fingerprints were found on a prescription bottle at a veterinary clinic (planted by Lionel Fusco at Finch's request), and immediately left New York ("Super").
After retrieving the drive that Mark earlier stole from Fujima Techtronics Stanton sends them to steal the car of two Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) agents.
(4.8 "Point of Origin") Martine is tasked by Greer to discover the identity of a woman (Sameen Shaw), who ISA operative Devon Grice allowed to escape a crime scene.
Blackwell can't complete his mission, but Mona tells him that his actions ultimately helped achieve the desired outcome: Following the outbreak, numerous civilians willingly went to clinics for vaccinations allowing Samaritan to secretly collect their DNA.
Collier and Vigilance use a computer virus to disable the power grid in New York City, so that they can capture Sen. Garrison, Control, National Security Adviser Manuel Rivera, John Greer and Finch.