Of course, my ultimate recommendation is that you watch every episode of all four seasons. Because not only is there usually a lot of character backstory being dished out via flashbacks, part of the fun of the show has been the escalation of stakes. And watching things grow out from a very basic level to the world-threatening dilemma the show's currently presenting to us as we get ready for the final 13-episode bow.
But here are the episodes you actually need to watch if you're going to try and join the endgame of Season 5.
Every previous episode of Person of Interest is currently available on Netflix.
(By the way, I've tried my best to be as non-spoilery as possible here. Which is why most of the photos are just of Jim Caviezel's Reese and Michael Emerson's Finch just staring off at things in the distance.)
Season 1
"Pilot"Of course you have to watch the first episode. Duh. It introduces us to former CIA killer John Reese (Jim Caviezel), mysterious billionaire Harold Finch (Michael Emerson), determined detective Joss Carter (Taraji P. Henson), and crooked cop Lionel Fusco (Kevin Chapman). Watch as Reese is transformed from a self-loathing homeless drunk into a weapon for justice after Finch offers him a chance to intervene on behalf of the "irrelevant" little guy who a massively powerful government surveillance program - The Machine - deems to be in danger (or deems to be the danger).
"Ghosts"
This is the follow-up episode, which helped set the pace for the series by demonstrating the "number of the week" format. It's not the best installment, case-wise, but it introduced us to the importance of flashbacks to the show. Like on Lost, this story device is an integral part of POI and here it was used to show us some backstory on Finch and The Machine.
"Witness"
This was the first time I sort of sat up and took more notice of Person of Interest as Reese took it upon himself to personally protect a school teacher (Enrico Colantoni) who witnessed a Russian mob killing. Lots of twists and turns.
(If you're willing) Also recommended: "Foe," "Get Carter," and "Number Crunch"
"Root Cause"
At first glimpse, this chapter seemed like a standard "number of the week" episode, but it wound up introducing a series villain who would become extremely important by the end of the season, and in the seasons to come.
(If you're willing) Also recommended: "Blue Code," "Flesh and Blood," and "Matsya Nyaya"
"Many Happy Returns"
This was a big Reese flashback episode, filling in a lot of gaps about how he got to be in the desperate and depressed state we found him in back in the pilot. It also shed some light on as to why Finch chose Reese as the one to help him save people.
"No Good Deed"
"Firewall"
"No Good Deed" and "Firewall" rounded out Season 1, as Reese once again found himself, like he was back in "Witness," surrounded on all sides by multiple enemies with a person he'd promised to protect.
Season 2
"The Contingency""Bad Code"
"The Contingency" and "Bad Code" kicked off Season 2 with somewhat of a two-parter. Even though, I've found, the POI season premieres aren't exactly the best episodes, I'm going to recommend them since they directly answer the cliffhangers left by the season finales. And here we also got some juicy backstory on one of the show's antagonists.
(If you're willing) Also recommended: "Masquerade," "Bury the Lede," and "The High Road"
"Prisoner's Dilemma"
Season 2 -- while introducing us the growing threat of the corrupt cop legion, HR (along with HR's actual leader) -- took Reese out of the game for a few episodes as he was both hunted by both the FBI and by his old CIA cohorts. Here, in "Prisoner's Dilemma," things came to a head as an incarcerated Reese (imprisoned under a fake identity) became a lead suspect in the federal hunt for the "Man in the Suit" (his vigilante label).
"Dead Reckoning"
This was the exciting follow up to "Prisoner's Dilemma," in which Reese's past caught up with him and turned him, literally, into a human bomb. It also marked the first appearance of yet another huge series bad guy.
"Relevance"
An excellent episode that actually felt like a backdoor pilot of sorts - if there were ever designs of giving Sarah Shahi's ass-kicking Sameen Shaw her own series, that is. So what was the big deal? Well, all our regular POI characters took a backseat to a whole new mission and a new protagonist... Who turned out to part of the same exact story we'd all been following, but just from a different angle.
"Trojan Horse"
"Zero Day"
"God Mode"
"Trojan Horse," "Zero Day," and "God Mode" closed out Season 2 with style, with actresses Sarah Shahi and Amy Acker becoming a part of the series in a major way as the events from back in "Dead Reckoning" caught up with our heroes and left them with a crippled Machine that was in danger of falling into enemy hands.
What Person of Interest episodes to watch from Seasons 3 and 4 over on the next page...
Season 3
Okay, here's the kicker. Season 3 is mostly serialized. So I don't readily recommend that you miss any of it, with possibly one or two exceptions. But I've tried my best here to streamline it."Liberty"
"Nothing to Hide"
Again, I'm recommending the season premiere, "Liberty," because of the fact that it's a follow-up to "God Mode," not because the "number of the week" is all that great. Also a long-standing enemy takes some pretty big steps toward becoming a team ally.
"Nothing to Hide," however, introduces a whole new supervillain group into the mix.
"Lady Killer"
Okay, so this is a mostly disposable episode, as far as the long-arc of the show goes. But the final ten minutes are jaw-dropping.
(If you're willing) Also recommended: "Razgovor," and "Mors Praematura"
"Endgame"
"The Crossing"
"The Devil's Share"
These three-episodes - "Endgame," "The Crossing," and "The Devil's Share" - felt like the Empire Strikes Back of the show's story. High stakes, pyrrhic victories, and big changes shook POI to its core. Little did we know that Season 3, as a whole, would wind up feeling like the "Empire" of the series. This trilogy is a must-watch.
"Lethe"
"Aletheia"
POI didn't really give its viewers a chance to breathe after the huge events that preceded "Lethe" and "Aletheia" - which themselves introduced us to the possibility of there being a rival supercomputer program called Samaritan, an AI once dreamed up by Finch's old MIT classmate, Arthur Claypool (Saul Rubinek). Many series villains converged here to create a big mess of violence and danger.
"RAM"
"RAM" was an amazing entry into the POI opus, though one that was especially rewarding to fans who'd watched all the episodes. It wasn't exactly a How It All Began entry, since the show already had been using flashbacks in almost every episode, but it did take us back a few years to show us the first "Man in the Suit" employed by Finch - a one Mr. Dillinger (Neil Jackson).
"/"
"/" - aka "Root Path" - Decima Technologies and Vigilance converge on Team Machine as Root must protect a janitor who has special access to a lab developing a supercomputing chip. A big episode for Root with regards to her character evolution and loyalty to the Machine.
(If you're willing) Also recommended: "Death Benefit"
"Beta"
"A House Divided"
"Deus Ex Machina"
And here we are at the end of Season 3, as Team Machine had to take on the threats of Decima, Vigilance and the possibility of Samaritan -- an active AI -- overtaking all of the country's surveillance. Years ago, I would have never expected the show to reach the crazy heights of "Beta," "A House Divided," and "Deus Ex Machina," which is a testament to the evolution of the series.
Season 4
Okay, so here's the deal with Season 4. Like Season 3, it's mostly serialized. Even more so, in fact. So, honestly, I don't recommend skipping any of it. But if you simply don't have the time..."Panopticon"
Notable because, as the season premiere, it directly addressed the fallout from Season 3's finale regarding where Team Machine landed in the aftermath, "Panopticon" also introduced a new seasonal villainous organization into the mix. A next-level intelligent street crew out to take over territory once controlled by HR.
"Nautilus"
By the second episode of Season 4, Team Machine was already fighting tooth and nail against Samaritan in puzzle-driven battle over a young genius girl's future. And soul.
"Brotherhood"
In one of the season's sparse breaks from Samaritan's threat, Team Machine went toe-to-toe with the Brotherhood - the nefariously clever gang introduced in the season premiere.
"Prophets"
Diving back into the deep end of the Samaritan pool, "Prophets" featured guest star Jason Ritter as a crackerjack political campaign manager caught in the middle of a lethal attempt at election tampering. A diabolical demonstration of Samaritan's far-reaching powers and a kick ass, action-packed ending.
"Honor Among Thieves"
Seemingly a Shaw-heavy "number of the week" episode, but an important one as it worked to introduce a couple of new Relevance characters who'd become important as the season progressed and the stakes escalated.
"The Devil You Know"
Since "The Devil You Know" kicks off with a huge gun fight that directly answers a cliffhanger, you may want to skip back and watch the episode right before it, "Pretenders." If not, you'll probably be fine as the very end of "Honor Among Thieves" might be all you need for an explanation.
Anyhow, the episode itself is an important, exciting Elias-focused episode that effectively kicks off a gang war. One that runs throughout the rest of Season 4.
"The Cold War"
"If-Then-Else"
"Control-Alt-Delete"
"M.I.A."
Billed as at the "Samaritan Trilogy" (actually a tetralogy, since "M.I.A." should be included), this string of episodes was Season 4's answer to the tragic "HR Trilogy" from the previous year. And what an ingeniously sad and smart run it was. Giving us, in fact, POI's best episode to date with "If-Then-Else." A non-stop, boundary-pushing thrill ride of a chapter designed to both entertain and crush us.
Plus, from a purity of concept level, these four episodes also contain some of the most imaginative, evolutionary work the series has ever done.
(If you're willing) Also recommended: "Q&A," "Blunt," "Skip," and "Search and Destroy"
"Terra Incognita"
A heartfelt Reese-driven "time out" episode before the final Season 4 crunch, "Terra Incognito" featured a phenomenal surprise in the form of a favorite character returning for a handful of superb scenes with Team Machine's stoic "Man in the Suit."
"Asylum"
"YHWH"
At the close out of Season 4, Team Machine desperately scrambled to save The Machine as Samaritan took aim at its ASI rival in a major way, determined to eliminate its main competition at the source. What would it take to save The Machine from being completely eliminated from the game board? Everything our heroes had, that's what. Person of Interest: Season 1-4 are all available on Netflix. Season 5 premieres Tuesday, May 3rd on CBS.
Matt Fowler is a writer for IGN. Follow him on Twitter at @TheMattFowler and Facebook at Facebook.com/Showrenity.