Lost, which aired from 2004 to 2010 for six seasons and over 100 episodes, followed the story of the survivors of Oceanic Flight 815 as they remained stranded on an island—and discovered there was a lot more to that island than it seemed, from the dangerous Others and the DHARMA initiative to the Smoke Monster and Man in Black.
From the pilot to the series finale, Lost presented some intense episodes, from the pilot's chaotic plane crash to the series finale's showdown between Jack and Locke as the Man in Black, with season premieres and finales, in particular, being packed with action and huge revelations. As the survivors of Oceanic 815 learned more about the island and its mysteries, the stakes became higher, and the show became about much more than just survival.
10 "Across the Sea"
Season 6, Episode 15 (2010)
Season 6’s “Across the Sea” provides the backstory for Jacob, played by Mark Pellegrino. His mother, while pregnant with Jacob and his brother, washed up on the island and encountered another woman, who killed her immediately after the boys were born and raised them as her own.
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Some of Lost’s most compelling episodes explored the history of the island and its most notable inhabitants, “Across the Sea” included. It’s clear from the start that the boys’ mother can’t be trusted, something they, too, learn as they uncover her dishonesty and manipulation and as her motives become more unclear.
9 "Exodus"
Season 1, Episode 23
In the three-part finale of Season 1, the French woman, Danielle Rousseau, played by Mira Furlan, arrives to warn the survivors the Others are coming, and they have three choices: “run, hide, or die.” She guides a group to the crashed ship Black Rock to retrieve dynamite so they can defend themselves and blow open the mysterious hatch to use as a hiding place. Meanwhile, Michael, played by Harold Perrineau, leads a group in an attempt to build and launch a raft to leave the island, and Charlie, played by Dominic Monaghan, and Sayid, played by Naveen Andrews, set out to rescue Aaron after he was kidnapped by Danielle.
“Exodus” is full of danger, starting with Danielle’s ominous warning and the volatile and ultimately deadly dynamite on the Black Rock, and with so much going on, it never lets up. The arrival of the Others—and the chaos they brought with them—was especially intense.
8 "Man of Science, Man of Faith"
Season 2, Episode 1
In the Season 2 premiere, as Locke, played by Terry O'Quinn, becomes more obsessed with the island’s hatch, Jack begins to question his motives. Locke and Kate, played by Evangeline Lilly, head inside, against Jack’s advice, and its contents are revealed.
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The tension in “Man of Science, Man of Faith” isn’t just from Jack’s frustration with Locke. The first few minutes set the tone for the entire episode, with a man going about his daily routine—until he’s interrupted by an explosion as the Oceanic survivors investigate.
7 "The End"
Season 6, Episode 17 (2010)
The series finale saw Jack, played by Matthew Fox, head to the heart of the island and battle it out with The Man in Black, in Locke’s body, to prevent him from destroying the island, while most of the remaining survivors hope to finally leave. Meanwhile, off the island in a flash-sideways, the survivors reunited.
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With so much at stake and everything coming to a head, the divisive series finale “The End” had plenty of tension. It was also an emotional finale, as the survivors’ reunion turned out to be happening in the afterlife—although this did not, as many have mistakenly interpreted, indicate that the survivors had really been dead for the duration of the series.
6 "The Incident"
Season 5, Episodes 17 and 18
In Season 5’s two-part finale, “The Incident,” Jack wants to change the future by detonating the Jughead bomb in 1977, and Ben, played by Michael Emerson, murders Jacob. Meanwhile, flashbacks reveal that many of the survivors had encounters with Jacob in crucial moments in their past, unaware of who he was.
“The Incident” features the show’s first look at Jacob and adds to the mystery of who he was and what his importance was. Most notably, though, the episode—and season—ended on a huge cliffhanger, as the effect of the Jughead bomb was left unknown.
5 "All the Best Cowboys Have Daddy Issues"
Season 1, Episode 11
After Charlie and Claire go missing, Jack and Locke set out to find them. It appears they were kidnapped by Ethan, played by William Mapother, someone they learn wasn’t on the passenger manifest and may be one of the Others.
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Lost became more harrowing as the Others were introduced, and “All the Best Cowboys Have Daddy Issues” showed just how dangerous they were and how far they were willing to go. The action starts immediately as Locke and Jack run through the jungle to find Claire and Charlie. The discovery of a nearly dead Charlie was shocking, and few scenes in the show were as emotional as Jack’s frantic attempts to revive him.
4 "Maternity Leave"
Season 2, Episode 15
When Claire’s baby, Aaron, suddenly gets sick, she becomes desperate to both find something to help him and unblock her memories of being kidnapped by Ethan. She travels with Kate and Rousseau travels to the site, and along the way, her flashbacks reveal what happened.
Claire’s desperation is palpable, especially as her memory returns in bits and pieces, each one more alarming than the last, starting with Ethan keeping her drugged at a DHARMA station. And while the quest for medicine for Aaron is compelling enough, Claire’s flashbacks are even more harrowing.
3 "The Constant"
Season 4, Episode 5 (2008)
As Sayid and Desmond travel to the freighter via helicopter, they’re caught in a thunderstorm, which particularly affects Desmond—it triggers his consciousness to travel back and forth between past and present, and the solution is a "constant," a person or thing he can latch on to.
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In “The Constant,” often considered one of the best episodes of the series, the transitions between past and present are jarring for both Desmond and the viewer, happening without warning and making Desmond increasingly confused. His encounter with someone experiencing the same thing demonstrates just how high the stakes are when it comes to stopping the jumps through time, and the intensity reaches its peak as the line rings when Desmond calls Penny, his constant.
2 "Through the Looking Glass"
Season 3, Episodes 22 and 23 (2007)
In the two-part Season 3 finale, Charlie is held captive in the underwater DHARMA station after volunteering to stop its jammed radio signal and ultimately sacrifices himself to save Desmond, played by Henry Ian Cusick. Meanwhile, Jack led a group of survivors to the island’s radio tower to use a satellite phone to communicate with a ship nearby.
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The whole episode is tense as things keep going wrong. Jack's success hinges on Charlie, and in the end, he not only learns they’ve been deceived by who’s on the boat, but he also warns Desmond in a final act before his devastating death. But it wasn't just the events on the island that were intense—in what was ultimately revealed to be a flash-forward, instead of the show's familiar flashbacks, Jack was struggling and desperate to return to the island.
1 "Pilot"
Season 1, Episode 1
In Lost’s two-part pilot, Oceanic 815, traveling from Sydney to Los Angeles, crashes on an island. Jack, a doctor, awakes alone in the jungle and heads towards the beach, where the plane is in pieces. Jack does his best to tend to injured survivors in the middle of the chaos, then sets out to find the cockpit to try and call for help.
Lost’s pilot episode wastes no time, and the first few minutes in particular are intense and harrowing. Just as things settle down, and the survivors are setting up camp, they hear strange sounds from the jungle, making it clear they haven’t crashed on an ordinary island.
