Before JJ Abrams was directing follow ups to the legacies of both Star Trek and Star Wars, he made his big splash with a dramatic television series ostensibly about the survivors of a plane crash, stranded on an uncharted island in the Pacific Ocean, desperately trying to both survive and get rescued.

Lost spanned six seasons and aired weekly on ABC from 2004 to 2010, and encomed over a hundred episodes. Most episodes focus on a key character on the island, and often reveal bits of dramatic irony via flashbacks. And each episode ends on a cliffhanger, which sets the stage for a continuous story—a daunting prospect for newbies to the series, sure to find themselves overwhelmed as to the inevitable commitment with which the series tempts its viewers. While by no means comprehensive, this chronological list explores the most memorable and accomplished of the series.

Here are the 13 Best Episodes of Lost.

Fair warning: there be SPOILERS here.

13. Pilot

The pilot to the series is not only crucial from a plot-oriented standpoint, but is itself a riveting and tense of the terror which grips the survivors of the transcontinental Oceanic 815 plane crash. Virtually from the start, we are thrown right into the action, as the de facto main character of Lost, Jack Shephard (Matthew Fox) opens his eyes in the jungle, and emerges on to a sunny beach of screams and engines firing. Lost smartly introduces characters via action here, not by having them walk onto the screen and simply say their names. We learn more about the key players by how they react to the shock of the traumatic event. Wounded from the crash, Jack implores a woman named Kate (Evangeline Lilly) to stitch him back up, though she is apprehensive at the prospect. While recalling an important story about his means to cope with his fear, Jack reveals that his life prior to the crash was that of a spinal surgeon, and the story becomes the first of many connections between Jack and Kate to follow, establishing trust between the two.

Originally conceived as a dramatic counterpoint to the reality show Survivor, elements of the struggle to survive in the wilderness are as integral to the plot as is the looming presence of the unknown force lurking in the trees. Establishing shots of survivors climbing the mountain to desperately try to get a clear signal for a transceiver recovered from the cockpit would not look out-of-place in a documentary, and give the show the sense of nature as an enemy, but still introduces some of the weirder elements for which the series would become known, such as a surprise ambush by a polar bear.

Split into two parts, the first half of the pilot is notably free from the flashbacks which would be the narrative hallmark of the series. That said, it is after Jack's recollections of his past that others follow, like Kate and Charlie (Dominic Monaghan), revealing key insight into these characters, often about a past they wouldn't want to share, one they must leave behind in order to survive. By the end of the pilot, we have what will become the core group of the survivors—even if we don't have everyone's names—and Lost firmly establishes the tropes of the series to follow, as well as portending future events, laying the groundwork for the elaborate mystery.

12. Tabula Rasa

"Tabula Rasa" continues the character development begun in the pilot, extending this to other key players and core characters for the series as a whole. Namely, we're given more of a formal introduction to Sawyer (Josh Holloway) beyond his initial confrontation with Sayid (Naveen Andrews). Sawyer begins as a stereotype, but over the course of the series becomes one of the most complex characters, with almost as diverse and interesting of a past as Kate. Speaking of Kate, "Tabula Rasa" begins a series of flashbacks to Kate's past, which is checkered, to say the least. As a fugitive, her flashbacks, in which she is forced to adopt aliases to evade capture, are reminiscent of other dramatic action series, such as The Fugitive or JJ Abrams' own Alias.

Additionally, other character qualities become established and maintained through the series. Hugo “Hurley” Reyes (Jorge Garcia) quickly becomes the beacon of warmth for the series, and is often the manifestation of “conscience” for others—an “angel on the shoulder.” Michael (Harold Perrineau) is desperate to prove himself as a father, an undercurrent which is felt in all of his interactions going forward. And Sawyer's cunning and aptitude for deception makes him the wild card in conflicts and desperate situations.

11. Walkabout

The first season of this series was simply so good, that several of the introductory episodes warrant inclusion here. While up until this point, the show has focused on Jack, Kate, Charlie, and a few others, "Walkabout" marks the proper introduction to one of Lost's most enduring and magnetic characters: John Locke (Terry O'Quinn). O'Quinn's addition to Lost's ensemble cast is arguably one of the series' triumphs; his portrayal of the determined and somewhat tragic survivor is—even if you're somehow not vested in the series as a whole—likely enough to keep your attention rapt, and his origin flashback establishes his role in the series as a major anchor character and a unique counterpoint to Jack.

There's a scene in the pilot where Locke describes backgammon to Walt (Malcolm David Kelley) as a game where “one is light, and one is dark;” it is a theme which pervades the series as a whole, and a thought which also describes Jack and Locke to an extent. They are both heroic characters, but from different backgrounds... and different walks of life. "Walkabout" establishes Locke as the “yin” to Jack's “yang.” For Jack, responsibility is a burden, but for Locke, it is an opportunity. While Jack is apparently straightforward about his past, Locke takes this disaster as a chance for a fresh start, allowing others perceptions of him to define him as a survivor and expert hunter, and not the boring man pitied by others in his past life.

10. Deus Ex Machina

As in "Walkabout," "Deus Ex Machina" is a “Locke” episode, since it focuses primarily on Locke, and the flashback element of the narrative is principally concerned with his past. Like many flashbacks, the events in the past parallel that of the present on the island. Locke and Boone (Ian Somerhalder) struggle to break into the recently discovered “hatch” found buried on the island, and the opening scene of Locke demonstrating the game of Mousetrap for a child represents this. It also represents how all of the pieces fit together—parts to the comprehensive whole—which, when complete, work together to achieve the goal; the same kind of metaphor could just as easily apply to faith, and that is the real theme at the crux of this episode of Lost.

The title—"Deus Ex Machina"—comes from a dramatic narrative convention, where a seemingly impossible situation is resolved by the arbitrary introduction of a new element. In Locke's flashback, this comes in the form of his sudden reemergence of his parents; in the present, it is a bit more literal, as a Beechcraft—a literal machine—is discovered via Locke's vision. There is irony in this episode, since elements which would be associated with providence are generally mechanical in nature, including Locke's father's dialysis machine, or even Sawyer's glasses. Even Locke's wheelchair proves to be emblematic of this.

Although Locke's best known catchphrase is “don't tell me what I can't do,” his real mantra is that everything happens for a reason. While not religious, it is clear that Locke is a man of faith, one which was cruelly capitalized on in his past—more than once—leading to events which ultimately broke his body, but not his spirit. Faith drives Locke, even when events are incomprehensible, such as his visions, which lead to Boone's unfortunate fate, a sacrifice on the altar of a higher purpose. This is the beginning of a supernatural element which becomes crucial to the series later. And all faith is a test, one which for Locke leads him to a final shot for the episode, which remains one of the most iconic for the series.

9. Man of Science, Man of Faith

The animosity and power struggle hinted at between Jack and Locke comes into sharper focus in the second season, evidenced by the title, which delineates Jack and Lock by their respective traits. With the Others lurking as an unknown threat to the survivors, Jack and Locke have debated the option of blowing open the hatch found in the jungle, but a significant reason for Jack's apprehension at trusting Locke's plan is unfolded in his flashback. Jack recalls a victim of a car accident named Sarah (Julie Bowen), whose spine is so damaged, that Jack refuses to offer her any hope that even with his best efforts that she will walk again, which prompts Jack's father, Christian (John Terry) to advocate the merits of hope as a healing tool; Hurley similarly chastises Jack for his shaky bedside manner on the island. Coming back to the title—"Man of Science, Man of Faith"—it becomes clear that while the episode primarily concerns Jack, these two concepts are not mutually exclusive.

Season 2 also establishes a trend for the bold openings for the seasons to follow. Here we see an unidentified man going about a daily routine, in a locale which might be anywhere in the world at any time. The scene is set to “Make Your Own Kind of Music,” performed by “Mama” Cass Elliot, and while seemingly anachronistic to the tension often established in the show, is effectively a “theme” for the character later revealed to be Desmond Hume (Henry Ian Cusick). Only when a massive explosion rocks this scene, do we understand that Lost has been performing one of many deceptions upon us, revealing by virtue of Jack and Locke staring down the canal into the hatch—now blown open—that this scene was right beneath their noses (and ours) the whole time.

There is a moment when Jack is running a tour de stade, trying to work out his inner demons, and finds Desmond doing the same. They talk about their respective drives and beliefs, the nature of miracles, and why Jack doesn't believe in them, whereas Desmond addresses Jack as “brother,” like a man possessed of holy influence. And when they part, Desmond says to Jack: “See you in another life, brother;” in effect, he does. Jack is entrenched in science, and has previously established he is not religious. And yet, be it science or faith, there is an arrogance in believing in something too rigidly, that it blinds you to another perspective, another possibility, another answer.

8. The Other 48 Days

The “Tailies”; love 'em or hate 'em, they afford the storytellers of Lost a unique opportunity to subvert our expectations of heroes and archetypes. Already introduced in part in preceding episodes—misinterpreted as “The Others” by survivors of the raft—the episode chronicles how the engers of Oceanic 815 traveling in the tail section survived, in contrast to the other survivors we have come to know. To an extent, it is like a “clip show,” except for a series that never existed, detailing the key days in their survival. In contrast, while the survivors of the midsection were challenged by the “smoke monster” early on, the Tailies had to contend with the presence of the true “Others” far earlier.

"The Other 48 Days" moves at breakneck speed, so we get acquainted with the key players via condensed scenes that establish their core traits. Ana Lucia Cortez (Michelle Rodriguez) is not the strong leader that Jack or Locke are, but she was trained as a cop and her deductive acumen is her strength, except when it is manipulated and warped into paranoia as the rigors of survival and presence of unknown quantities claws at her mind. Characters mentioned in ing in season 1, like Bernard (Sam Anderson), make their appearance here, as do characters like flight attendant Cindy (Kimberley Joseph), who gave Jack his extra bottles of vodka in the pilot flashback. Moments like this further cement an interconnectedness that is a core theme of Lost. There's even a clever callback to "Deus Ex Machina," when after Boone sends the transmission from the Beechcraft, it is in fact Bernard who answers.

7. One of Them

In keeping with Lost's playful subversion of our expectations, "One of Them" plays a great trick on us. Formally, it presents itself as another flashback episode for Sayid—once concerning themes of loyalty and deception—but there is a secret lurking, waiting to unleash a crucial character into the Lost mythos. Meet Henry Gale (Michael Emerson). The interconnectedness of Lost is key here; Henry Gale is found by Danielle Rousseau (Mira Furlan), a survivor of the island for sixteen years, who previously abducted Sayid and tortured him in an ironic parody of his own skills acquired as a torturer, which he acquired during a time portrayed in his flashback in "One of Them." Danielle has been searching for her daughter, Alex, a connection which only becomes clear in seasons to come, but is established here.

As mentioned, Sayid learns what is necessary to become a torturer during his time in the Iraqi Republican Guard during the First Gulf War; but it is not his country which endows him with this unique skill set, but his American captors who convince him that his captured superior officer is not worthy of the loyalty Sayid has prided himself on possessing. Danielle claims Henry Gale is not what he seems; so when Sayid takes him back to the hatch—a new base of operations for some of the survivors—his presence forces a confrontation between Locke and Jack as to what they will do with him, leading to Sayid torturing him for information about who he “really” is. Torture is generally regarded as unethical, but so is deception. The question posed here is: which is worse in the end? This is the question which defines the “survivors” and their ephemeral foe, “The Others.”

It was said by the creators that Michael Emerson's role was expanded on greatly as a result of his monumental performance in "One of Them," and he ended up becoming a series regular. It's a convincing assertion. Henry Gale's presence is a skillful lynchpin. By merely being there, he forces a schism between Jack and Locke to rupture wider; just what The Others would want to happen. And while this list is composed of fairly serious episodes, this one does feature a humorous and initially lighthearted subplot where Sawyer recruits Hurley to help him hunt a noisy tree frog in Looney Tunes fashion... until Sawyer catches it. Between this and Sayid's ission to Henry Gale, it becomes clear that when forced to endure under foreign environs, one's true colors come out... save for those with a natural predilection for hiding in plain sight.

6. Not in Portland

Although Juliet made her debut in true Lost fashion at the beginning of season 3, here is where we get the crucial, sorrowful flashback to this intriguing character. Juliet is a favorite because she is not like the other Others, if you'll excuse the phrase. She is consistently pulled in all different directions, and comes to be viewed as a pariah among both the survivors and the Others. She is a woman of science, a fertility doctor who is under the impression she will be contributing to a cause to aid her sister's desire to become pregnant. But before she can back out, she finds herself among wolves, and must use her cunning to survive, knowing that honesty is a luxury she cannot afford.

From the opening, the question we have is how Juliet could go from being so sympathetic to being so ruthless, between the flashback to her sister in Miami and her bargaining play with Jack as Ben bleeds out on the operating table, so that Kate and Sawyer can make their escape from their prison cage. Juliet appears out-of-place among the Others, just as she was displaced in her life prior to the island, a trend which continues for her throughout the series. Juliet's past shows her as mousy and browbeaten by an ex-husband uninterested in anything but himself. In her flashback, she is approached by Richard Alpert (Nestor Carbonell) to their research group, but she painfully its the grip her ex has over her, and half-jokingly its the only way she could leave is if he were hit by a bus. After he actually is hit by a bus, she comes to the conclusion that sometimes the right people have to die to make the world a better place.

5. Through the Looking Glass

"Through the Looking Glass" is the real turning point for Lost, one which upends many of the foundations the series has been built upon, unsettling our expectations. It begins with a bearded Jack, disheveled and morose, his appearance and demeanor already a clue for fans that something is cooking in the soup pot of mind-blowing shockers. This transition also establishes the island as something special, core to the being of its residents which will not be denied. Scenes are intercut between this Jack and the one described by the mystery woman, Naomi (Marsha Thomason), as “Moses”, leading his people to the promised land before an impending attack by the Others, their confrontation coming to a violent head. This parallel is more pronounced as Ben appears as a tyrannical Ramses, chasing down the survivors, determined to prevent them from escaping for reasons which become clear in time.

This episode also showcases Charlie's moment of redemption, confronting the terror of the prophesy Desmond revealed to him about his imminent death. It is the supreme moment of heroism for the man who was at the beginning of the series just a rock star junkie, transformed and reborn. And of course, that the code is a send up to The Beach Boys makes for a clever turn for the ex-bassist of Drive Shaft.

Of course, the title is a reference to Lewis Carroll's followup to Alice in Wonderland, as well as the Dharma station that Charlie must infiltrate to allow the survivors a chance to Naomi's boat, not to mention the sorrowful, ironic means by which Charlie gives Desmond his last, crucial message. It also concerns Jack, shattered by something he has lost. Jack reflects on his past—what he has left behind, the friend who he learned suddenly died, one where he is the only attendant at the viewing. It is, like the book, also like a sequel, a story about returning to the strange wonderland, where there may have been so much calamity, but also a sense of life that makes the real world a mere reflection by comparison.

4. The Constant

Widely regarded as the “best” episode in the series—and one of the best episodes in any dramatic series—"The Constant" cleverly subverts the convention of the flashback from the start, as Desmond's consciousness bounces between his past and the “present' as we know it. Desmond's story has frequently been at the head of the unexplained phenomena of Lost, first through his visions and the mysteries of the island, monitored in the hatch, but now in the realm of hypothetical science, a theme largely present in the series. One of the few benevolent freighter people, Daniel Faraday (Jeremy Davies) tries to explain the phenomenon to Jack and Juliet, observing that their “perception” of time is not the reality of it, which hints at the idea of time as a malleable force, not merely a straight line. The episode also introduces us to the sinister mercenary, Keamy (Kevin Durand) who, unlike Ben, is a thoroughly cold-hearted and cruel villain.

Daniel explains to Desmond the nature of the constant, telling him to find him in the past, to create a temporal connection, a link, a means to cope with the conflicting fourth dimension. It is a bridge between the past and a present, and a metaphorical one for the narrative structure of the series as a whole. Faraday explains to Desmond that in order to stabilize his consciousness, he needs something constant between times, advise which paradoxically makes him into who he is. The episode is a masterpiece of cause and effect, with Desmond as the pendulum swinging back and forth. "The Constant" also contributes other crucial nuggets about the connection between Charles Widmore (Alan Dale) and the island, adding more pieces to the puzzle, clarifying the big picture about what the island is and what it means to those who seek it. There is also a call back to the end of season 3, how Charlie saved Desmond, who in turn previously saved Charlie. "The Constant" is about the connections we make with one another, be it a phone call, a friend, a brother, or a lover, the constants in our lives.