- "Man of Science, Man of Faith"
One of the castaways is chosen to descend into the hatch, and Shannon stumbles upon a shockingly familiar face in the jungle. The band of friends, family, enemies and strangers must continue to work together against the cruel weather and harsh terrain if they want to stay alive. But, as they have discovered during their 40-plus days on the Island, danger and mystery loom behind every corner, and those they thought could be trusted may turn against them.
With the abduction of Walt fresh on their minds and their raft destroyed, Michael, Sawyer and Jin fight for their lives and discover a new predator in the roiling ocean. Meanwhile on land, Locke must descend into the Hatch when one castaway goes missing inside.
Jack, Locke and Kate learn more secrets about the Hatch. Meanwhile, after being beaten and taken captive, Sawyer, Michael and Jin wonder if their captors are fellow survivors or the dreaded "Others".
- "Everybody Hates Hugo"
Disturbing memories from Hurley's past cause him to struggle with a task he's assigned inside the Hatch. Meanwhile Sawyer, Michael and Jin discover the identities of their captors, and Claire uncovers a shocking piece of information about the fate of the raft.
- "...And Found"
Michael sets off into the jungle by himself determined to find Walt, but discovers that he is not alone. Meanwhile, Sawyer and Jin are ordered by their captors to take them to their camp, and Sun frantically searches for her missing wedding ring.
Sawyer's wound becomes life-threatening as he, Michael and Jin make their way through the interior of the Island with the tail section survivors. Meanwhile, Shannon is once again haunted by visions of Walt, and Charlie becomes jealous of Locke's interest in Claire.
- "The Other 48 Days"
The harrowing first 48 days in the lives of the tail section survivors are revealed.
Tempers flare when Ana Lucia and her group stumble upon Sayid and the other castaways.
- "What Kate Did"
Kate's original crime that started her life on the run is revealed. Meanwhile, the survivors lay one of their own to rest, Kate sleeplessly watches over a feverish Sawyer, and Mr. Eko has a surprise for Locke regarding the Hatch.
- "The 23rd Psalm"
Mr. Eko interrogates Charlie about the Virgin Mary statue, Claire begins to lose faith in Charlie when she discovers his secret, and Jack is an interested observer when Kate gives the recovering Sawyer a much-needed haircut.
- "The Hunting Party"
Jack, Locke and Sawyer pursue a determined Michael after he heads into the jungle toward the dreaded "Others" in search of Walt. Meanwhile, Sun has a surprising reaction to Jin's desire to join the search party, and Hurley and Charlie commiserate over the age-old conundrum of "what women want".
- "Fire + Water"
When Charlie's vividly surreal dreams lead him to believe Claire's baby, Aaron, is in danger, Locke suspects Charlie may be using again. Meanwhile, Sawyer encourages Hurley to act on his attraction to Libby.
- "The Long Con"
Survivors fear that "The Others" may have returned when Sun is injured during a failed kidnapping attempt.
- "One of Them"
When Rousseau leads Sayid to a mysterious captive in the jungle, he becomes determined to find out if he is one of "The Others". Meanwhile, Sawyer discovers Hurley's potentially devastating breech of the survivors' trust and blackmails him into helping track an elusive island creature that won't leave Sawyer alone.
- "Maternity Leave"
A desperate Claire, along with Kate and Rousseau, attempts a return to the scene of her kidnapping where she believes she might find the cure for Baby Aaron's mysterious illness. Meanwhile, Jack and Locke must keep their prisoner a secret from the rest of the survivors. This episode is unique in that all of Claire's flashbacks were her experiences on the Island while she was abducted by Ethan, not of her life before the crash.
- "The Whole Truth"
Sun wrestles with the thought of telling Jin a newfound secret that threatens to upset the entire balance of the survivors' community. Meanwhile, Locke enlists Ana Lucia to interrogate the prisoner in order to extract more information than he, Jack or Sayid could.
When the Hatch suddenly takes on a life of its own, Locke is forced to enlist the help of an unlikely ally. Meanwhile, Ana Lucia, Sayid and Charlie go off into the jungle to find out the truth about Henry.
Libby lends Hurley support when he begins to think the Island is having a strange effect on him, and Locke's sense of purpose is shaken when the prisoner provides new information about the Hatch.
Rose is surprisingly and vehemently opposed to Bernard's plan to create an S.O.S. signal; romantic sparks are rekindled between Jack and Kate when they trek into the jungle to propose a "trade" with "The Others"; and Locke begins to question his faith in the Island.
- "Two for the Road"
Jack and Kate bring an exhausted Michael back to the camp, and with him, news about "The Others". Meanwhile, Ana Lucia attempts to get the prisoner to confess, and Hurley plans a surprise date for Libby.
Mr. Eko enlists Locke to help find a secret location he believes houses answers to the Island's mysteries. Meanwhile, Jack and the other survivors struggle to cope with the horrific situation in the Hatch.
- "Three Minutes"
A determined Michael convinces Jack and several castaways to help him rescue Walt from "The Others". Meanwhile, Charlie struggles with Eko's decision to discontinue building the church.
- "Live Together, Die Alone"
After discovering something odd just offshore, Jack and Sayid come up with a plan to confront "The Others" and hopefully get Walt back. Meanwhile, Eko and Locke come to blows as Locke makes a potentially cataclysmic decision regarding the "button" and the Hatch.