Main (Reese),
Michael Emerson (Finch), and
Kevin Chapman (Fusco) (Carter) (Root) (Shaw) •
Jim Caviezel as
John Reese: a former
United States Army Special Forces soldier and later a
CIA SAD/SOG operative in the
Special Activities Division •
Michael Emerson as Harold Finch: a reclusive, security-conscious, and intensely private billionaire
software engineer. His real name is unknown and he has many aliases (most commonly Harold Wren), using various species of birds as the surname. •
Taraji P. Henson as Joss Carter (seasons 1–3; guest season 4): a
New York Police Department detective stationed at the NYPD's 8th Precinct and a member of the NYPD's Homicide
Task Force. Carter is a former US Army
lieutenant and
interrogation officer who served in the
4th Infantry Division and passed the
bar exam in 2004, but gave up practicing law to return to police work. •
Kevin Chapman as Lionel Fusco: a reformed
corrupt NYPD detective whom Reese blackmails into being a source inside the NYPD and later arranges for him to be transferred into Carter's 8th Precinct and reassigned to the Homicide Task Force so that the two end up working together. •
Amy Acker as Root Samantha Groves (seasons 3–5; guest season 1; recurring season 2): a genius
hacker obsessed with the Machine. She later becomes the only person able to communicate directly with the Machine, when it chooses her as its "analog interface". •
Sarah Shahi as Sameen Shaw (seasons 3–5; recurring season 2): a former
United States Marine and later a US Army
ISA operative and assassin who was working for Northern Lights, where she unknowingly dealt with the "relevant" numbers generated by the Machine
Recurring •
Brett Cullen as Nathan Ingram, Finch's collaborator on the Machine who died in a
suicide bombing attack set up by the government. Ingram acted as the interface between the government and his company while the Machine was under development. Finch and Ingram became best friends while they both attended the
Massachusetts Institute of Technology. •
Carrie Preston as Grace Hendricks, Finch's fiancée who believes him to be dead following the ferry bombing that killed Ingram •
Paige Turco as Zoe Morgan, a "
fixer" who specializes in
crisis management. Finch and Reese first meet her as a person of interest. Later, she works with them on cases that require her skills. She and Reese have an apparently sporadic romantic relationship. •
Ken Leung as Leon Tao, a former
financial criminal and three-time person of interest who has assisted in some cases with his
forensic accounting skills. He has a penchant for get-rich-schemes which always land him in difficulties with
gangsters. •
Brennan Brown as Nicholas Donnelly, an FBI special agent who becomes interested in Reese when his case crosses one of Reese's. He periodically offers Carter the opportunity to work with him as he pursues Reese. •
Luke Kleintank as Caleb Phipps, a genius teenager with a difficult past. Phipps later returns as a successful computer coder. •
Susan Misner as Jessica Arndt, Reese's deceased lover. After Jessica's relationship with Reese ended, she married another man, but remained in contact with Reese. •
Wrenn Schmidt as Iris Campbell, a
therapist assigned to speak with Reese, working undercover as NYPD Detective John Riley, after his involvement in shooting incidents as a police officer. At the end of the episode "Skip", she develops a romantic relationship with Reese. •
Jimmi Simpson as Logan Pierce, a tech billionaire and person of interest in the middle of the second season, who returned towards the end of the fifth season and, together with two other former persons of interestJoey Durban and Harper Roseforms a second team also working for the Machine, that is based out of
Washington, D.C. •
Annie Ilonzeh as Harper Rose, a
drifter and opportunistic
con artist who first appears in "
Blunt" as a person of interest when she tries to independently double-cross both a drug cartel and the Brotherhood. At the end of the episode "
Skip", it is revealed that the Machine is starting to anonymously use her as an asset. In "
Synecdoche", it is revealed that Harper has become part of a second team working for the Machine in Washington, D.C., with former persons of interest Joey Durban and Logan Pierce. •
James Carpinello as Joey Durban, one of the machine's first numbers in the first season who returns at the end of the series to reveal that hetogether with two former persons of interest, Harper Rose and Logan Piercehas formed a second team in the nation's capital •
Alex Shimizu as Tatsuro Daizo, a programmer recruited by Root to help protect the Machine's assets from Samaritan •
Michael Esper as Jason Greenfield, a hacker and former member of Vigilance that becomes an asset of the Machine •
Joseph Mazzello as Daniel Casey, a hacker formerly targeted by the CIA for discovering the existence of the Machine. He is recruited as an asset to protect the Machine's operatives from Samaritan.
Government The following characters are tied to a government project related to the development and use of the Machine: •
John Doman as Ross Garrison, a
US Senator charged with overseeing the Northern Lights project •
Elizabeth Marvel as Alicia Corwin, a
liaison between Ingram and the government while the Machine was being developed and a former member of the
National Security Council •
Camryn Manheim as Control, the woman who is the head of the ISA's operation (code-named "Northern Lights") regarding the Machine. To protect the Machine, she sanctioned the suicide bombing that killed Ingram and caused Finch's injuries. When the plug is pulled on "Northern Lights", she is unwittingly installed as a puppet heading Samaritan, a position with which she becomes more and more uneasy. •
Boris McGiver as Hersh, the Special Counsel's enforcer, a former member of the ISA •
Jay O. Sanders as the Special Counsel, a shadowy figure from the
Office of Special Counsel who appears to be coordinating the activity regarding the Machine and sees Reese as a threat •
Cotter Smith as Denton Weeks, the official who commissioned the development of the Machine while he was a
Deputy Director of the
NSA •
Jacob Pitts as Henry Peck, an NSA analyst who stumbles upon the existence of the Machine, putting him in grave danger
NYPD •
Sterling K. Brown as Cal Beecher, an NYPD
Narcotics detective with whom Carter had begun a relationship. Beecher is Alonzo Quinn's godson but was unaware of Quinn's activities. •
Anthony Mangano as Kane, an NYPD homicide detective with whom Carter and Fusco periodically work •
Michael McGlone as Bill Szymanski, an NYPD
Organized Crime Unit detective with whom Carter sometimes works •
Ned Eisenberg as Joseph Soriano, an
Internal Affairs detective investigating Fusco for corruption •
Adria Arjona as Dani Silva, an undercover Internal Affairs detective whose investigation attracts the attention of the Brotherhood
HR The following characters are involved in the HR storyline, in which a group of corrupt police officers and public officials work to control organized crime in New York: •
Robert John Burke as Patrick Simmons, a uniformed NYPD patrol officer who is a
right-hand man to Quinn and HR's
second-in-command. He handles HR activities on the street level. • John Fiore as Womack, the Homicide Division captain and Carter and Fusco's supervisor •
Michael Mulheren as Arthur Lynch, an NYPD captain and major figure in HR with whom Fusco appeared to be working in the first season •
Clarke Peters as Alonzo Quinn, the mayor's chief of staff and the head of HR •
Al Sapienza as Raymond Terney, an NYPD detective working for HR who periodically crosses paths with Carter • Brian Wiles as Mike Laskey, a rookie NYPD officer (and mole for the Russian mob) affiliated with HR who is installed as Carter's new partner after she is demoted to officer for getting too close to HR •
James Hanlon as James Stills, a corrupt NYPD Narcotics detective who orders a hit on Reese
The Mob •
Enrico Colantoni as Carl G. Elias, a nascent crime boss and the illegitimate son of Mafia don Gianni Moretti. Elias is determined to revive and reunite
the Five Families of
New York City and to purge
Brighton Beach in
Brooklyn of the expanding grip of the
Russian mob, in particular the Yogorov crime family headed by Peter Yogorov. Although not a "good" man, Elias is generally seen as a source of order and stability in the underworld and considered the lesser of two evils. •
David Valcin as Anthony S. "Scarface" Marconi, Elias' lieutenant, principal enforcer and close friend. He is in charge of executing Elias' directives, speaking for Elias, and operating in his place. He occasionally acted as Elias's eyes and ears on the ground, especially when Elias was incarcerated. •
James LeGros as Bruce Moran, Elias's accountant and close friend of both him and Anthony Marconi from boyhood. He attempts to hold Elias's empire together while Elias recovers from the Samaritan attack. •
Mark Margolis as Don Gianni Moretti, a mob boss and leader of one of the five Italian crime families •
Morgan Spector as Peter Yogorov, leader of the Russian mob, specifically the Yogorov crime family, and Elias' nemesis for control of New York's criminal underworld
CIA The following characters are part of Reese's backstory relating to his time with the CIA: •
Michael Kelly as Mark Snow, a CIA Agent who once worked with Reese •
Annie Parisse as Kara Stanton, an ex-CIA Agent and Reese's former CIA partner who was widely believed to be dead, but is later recruited by Decima Technologies •
Darien Sills-Evans as Tyrell Evans, a CIA Agent working with Snow
Decima Technologies The following characters are involved in the Decima Technologies storyline, a shadowy organization that is in possession of the Samaritan AI: •
John Nolan as John Greer, a mysterious, arrogant, former
MI6 Agent who is the director of operations for Decima Technologies and runs the Samaritan AI •
Julian Ovenden as Jeremy Lambert, an operative for Decima Technologies, and Greer's right-hand man •
Cara Buono as Martine Rousseau, a psychotic former investigator for the
United Nations, now a Samaritan operative •
Oakes Fegley as Gabriel Hayward, a young boy who acts as Samaritan's "analog interface" •
Joshua Close as Jeff Blackwell, an ex-con who is recruited by Samaritan • Robert Manning Jr. as Zachary, an operative for Decima Technologies who later becomes a Samaritan agent •
Leslie Odom Jr. as Peter Collier, the leader of Vigilance, a violent organization which professes to protect people's privacy. •
Quinn Shephard as Claire Mahoney, a former college student looking for a purpose when she finds Samaritan
The Brotherhood The following characters are involved in the Brotherhood drug gang storyline: •
Winston Duke as Dominic "Mini" Besson, the leader of the Brotherhood gang •
Jamie Hector as Link Cordell, a violent gang member and Dominic's right-hand man •
Jessica Pimentel as Floyd, another of Dominic's higher-ups, often appearing in place of Link
Computer systems • The Machine is an
artificially intelligent system, created at the request of the U.S. government, to sift through the data collected by NSA
mass surveillance. It is able to accurately predict premeditated
lethal crime by analyzing the data from all surveillance cameras and electronic communications worldwide which are fed to it by arrangement with the NSA. • Samaritan: Initially developed by Arthur Claypool (a former
MIT classmate of Finch's and Ingram's) at the
NSA, Samaritan was the result of a second project that was terminated by Congress when the Machine was developed first. Unlike the Machine, Samaritan is designed as a more open system rather than a
black box, lacking the precautionary restrictions Finch had built into the Machine, and can be directed at specific targets. ==Episodes==