The series was renewed for a fourth season in March 2014[1] and stars Jim Caviezel, Kevin Chapman, Amy Acker, Sarah Shahi and Michael Emerson.

The series revolves around a team led by a mysterious reclusive billionaire computer programmer, Harold Finch, who has developed a computer program for the federal government known as "the Machine" that is capable of collating all sources of information to predict terrorist acts and to identify people planning them, as well as detecting all lesser crimes, known as "irrelevant" crimes.

The focus of the season involves the team's fight against Samaritan, a mass surveillance system that aims to destroy the Machine.

[2] The season received highly positive reviews from critics, with the writing, performances and Samaritan's thematic value garnering praise.

They continue to work on cases, but must now also evade Samaritan, which lacks the restrictions and human-oriented perspective Finch built into the Machine, and which is seeking to resolve perceived problems of human violence by reshaping society, sometimes violently.

Samaritan manipulates the NSA, fixes elections, triggers stock market crashes, kills those seen as threats, changes data to gain results perceived as beneficial, buys useful corporations, and continues building an organization to support its own goals.

But because Shaw's country presumed her dead and she kind of had to escape her own 'death', I never pictured it as, 'OK, she's part of a team' but 'She needs extra eyes, ears and hands working to help keep her safe.'

[33] Shahi reinstated that it wasn't a permanent exit, claiming that the point of the episodes were to give more priority to the team in their fight against Samaritan.

"[37] The episode featured the shooting of Dominic Besson and Carl Elias, with the latter playing a very important role on the series since the first season.

[43] In July 2014, Cara Buono joined the series in a recurring role as Martine Rousseau, "a femme fatale who's uniquely qualified to navigate the new world order of Season 4 of the procedural drama.

"[27] In August 2014, Monique Gabriela Curnen joined the series in a recurring role as Captain Felicia Moreno, "Fusco’s latest (and hopefully not corrupt!)

[46] In August 2014, it was announced that Jason Ritter would guest star as Simon Lee, "a whip-smart, political Wunderkind with an incredible gift of foresight.

"[47] In November 2014, Blair Brown joined in a guest role as Emma Blake, "an elegant and warm former public school teacher.

"[49] In the same month, Katheryn Winnick was announced to guest star as Frankie Wells, "a resourceful, relentless bounty hunter who enjoys her job of chasing down bad guys perhaps a bit too much.

"[58] Nolan talked about "Control-Alt-Delete", saying "Right when you get to a really really juicy part of the story where the audience can't wait to find out exactly what happens next, you switch gears and do something different.

The site's critical consensus is, "Thought-provoking, grounded sci-fi makes season four of Person of Interest as compelling as it is timely.

"[89] Mike Hale of The New York Times wrote, "The Season 4 premiere... is a decent demonstration of the show's charms: some action, some humor, some dystopian high-tech intrigue and an ensemble of actors who seem to be having fun and whose characters actually seem to care for one another.

In that respect, it's a much more disciplined show than The X-Files, which only returned to its ongoing alien colonization storyline for a handful of episodes each season and very quickly ran out of anywhere to go with it.

But Person of Interest has a couple of decades of TV serialization post-X-Files to draw upon, time that has been spent in figuring out how best to unspool these stories so they can keep going and going and going.

Fowler gave the episode a perfect rating of 10 out 10, indicating it to a "masterpiece", and praised the simulation format, the action scenes, the emotional value, and the ending.

[94] Shant Istamboulian of Entertainment Weekly lauded Emerson's performance in the flashbacks and felt the season marked the series' "creative peak".