In 2004, ABC’s groundbreaking show, Lost, introduced viewers to the survivors of the crashed Oceanic 815 flights and the island they were stranded on. It became clear that the show was more than a simple, straightforward survival story. Instead, it was more supernatural and sci-fi – although its heart was its characters – and it’s kept people talking in the decade-plus since it came to an end.
Over its six seasons and 121 episodes, fans of Lost worked to untangle numerous mysteries tied to the island and its history, like the identity of the mysterious, dangerous Others to the origins of the Smoke Monster, and the significance of infamous numbers. On top of that, one mystery often led to another, and things got more convoluted as the show’s mythology expanded and explored time travel and alternate timelines. The show played with its own format, switching from flashbacks to flash-forwards, and flash-sideways, sometimes using more than one in a single episode. As a result, viewers were often left with more questions than answers, and sometimes it all came down to a single notable moment recontextualizing an entire episode. And yet, some of the show’s most confusing episodes were also some of its best.
Season 2, Episode 21 (2006)
In Season 2, Episode 21, “?”, Eko has dreams about his brother, Yemi, leading him to help Locke, who Yemi insists has “lost his way.” Eko and Locke set out to find Yemi’s location, a question mark shown on the blast-door map, and are at odds on the journey.
DHARMA was still very much a mystery at this point in the series, and they discover a new station with surveillance that feeds into all the others. They also find an orientation video saying it’s designed to observe a psychological experiment, offering up very little new information.
9 “LA X”
Season 6, Episode 1 (2010)
In the Season 6 premiere “LA X,” the survivors are shown in a timeline where Oceanic 815 never crashes and instead lands safely. At the same time, they continue their lives on the island after Juliet detonates the bomb in the Season 5 finale.
“LA X” introduced the idea of parallel universes, called “flash-sideways” by the creators and fans—but things weren’t quite right. As often happened on Lost, it raised more questions, and more is revealed about the true nature of what was going on. On top of that, Locke was revealed to be the Man in Black.
Season 5, Episode 3 (2009)
Desmond goes to Oxford to find Daniel’s mother, who might be able to stop the island as it moves through time. On the island, the group encounters The Others in the 1950s – including Richard, who looks exactly the same.
The island’s travels through time continue in “Jughead,” is similar to “Because You Left”. It seems as though Daniel is already familiar with the past of The Others. In addition, the episode made the character of Richard more of a mystery, and each piece of information Desmond unearthed led to more mystery.
7 “There’s No Place Like Home”
Season 4, Episode 13 (2008)
In the three-part Season 4 finale “There’s No Place Like Home,” the Oceanic survivors team up with The Others against a freighter that has come to the island. Meanwhile, in flash-forwards, the Oceanic 6 are reunited with their families, and Jack visits a funeral home.
“There’s No Place Like Home” had a few revelations that made for some confusing moments, like Ben moving the island. But perhaps the biggest one was the identity of who was in the coffin Jack was visiting—Locke.
6 “Flashes Before Your Eyes”
Season 3, Episode 8 (2007)
Desmond has been acting strange since The Swan Station imploded and appears to have the ability to predict the future. However, he doesn’t seem to be able to distinguish it from the present. In order to get the truth out of him, Charlie and Hurley set out to get him very drunk.
The bulk of “Flashes Before Your Eyes” is a flashback—sort of. In this case, Desmond is actually reliving his past, and it’s revealed that after he turned the failsafe key, he was transported back to his life in London for a few days. Moments like Desmond spotting Charlie busking on the street make it unclear what was happening or why. The episode also wouldn’t be the last time viewers see Desmond involved with time or his ex-girlfriend Penny’s importance.
5 “The Constant”
Season 4, Episode 5 (2008)
As Desmond and Sayid travel to the freighter via helicopter in a lightning storm, the journey has a strange, unexpected effect on Desmond. His consciousness starts shifting between the past and present, and the one thing the two have in common is Penny. Meanwhile, on the island, Daniel reveals to the rest of the group that time works differently on the island.
The compelling, emotional plot makes “The Constant” one of the best episodes of the entire series and is similar to “Flashes Before Your Eyes” in that Desmond was actually experiencing another timeline. Here, the first instance of his shift was jarring and disorienting, since at first, it seems like a typical flashback. It quickly became clear that’s not the case, but it took some time to unravel what happening and why.
4 “Ji Yeon”
Season 4, Episode 7 (2008)
Sun-Hwa learns she is pregnant—and one of the mysteries of the island is the fact that pregnant women always die. With the survivors split into two camps, one led by Locke who is unwilling to leave the island, Sun decides to go to Locke’s camp. Meanwhile, Juliet stresses that if they’re rescued, Sun-Hwa needs to go. In desperation, Juliet tries to appeal to Jin, going so far as to tell him Sun-Hwa had been with another man just before the flight crashed on the island.
Similar to “Through the Looking Glass” in the previous season, “Ji Yeon” played with the familiar flashback/flash-forward format, this time with Sun-Hwa and Jin. Sun-Hwa was about to give birth and Jin rushed to get to the hospital. It seems as though their scenes were in the same timeline, but Jin’s scenes were flashbacks and Sun-Hwa’s flash-forwards, making for a confusing moment for viewers.
3 “Because You Left”
Season 5, Episode 1
As a result of Ben moving the island, the survivors who are left there keep skipping through time at random, and Daniel manages to get a message to Desmond. Meanwhile, Ben and Jack work to reunite the Oceanic 6 survivors – Locke’s dead body included – to save those left behind.
“Because You Left” is best summed up by Sawyer’s confused “What?!” as Daniel explains what’s happening, comparing it to a skipping record. On top of that, Daniel was also shown to be with the DHARMA Initiative at the beginning of the episode without explanation, as engineers came upon energy capable of manipulating time, and the usual rules of time travel apparently don’t apply to Desmond.
2 “Through the Looking Glass”
Season 3, Episode 22 (2007)
In the two-part Season 3 finale, “Through the Looking Glass,” the survivors face off against The Others. Meanwhile, Charlie and Desmond head to an underwater station to turn off a signal jamming the radio tower as Jack leads a group waiting for them to succeed.
“Through the Looking Glass” is highly regarded overall, but it’s notable for being the first to use a flash-forward instead of a flashback—although that wasn’t clear until the very end. That reveal, featuring an emotional Jack screaming, “We have to go back,” is huge and just raises more questions.
1 “The End”
Season 6, Episode 17 (2010)
Lost culminates in the finale “The End”, with Jack making his way to the heart of the island in order to protect it. However, Locke—now the Man in Black—worked to destroy it. Meanwhile, in a flash-sideways, Desmond reunited the passengers of Oceanic 815.
“The End” remains a divisive TV finale, largely due to the fact that many fans misunderstood the scenes of the survivors in the afterlife as confirmation that they were dead the whole time, from the pilot on. But the great Drive Shaft gig in the sky is a meeting place for them after their eventual deaths. They were destined to reunite and move on together.
NEXT: Every Season of ‘Lost,’ Ranked From Downright Unhinged to Iconic Television