One of the castaways is chosen to descend into the mysterious hatch, and Shannon stumbles upon a shockingly familiar face in the jungle.
After the raft explodes, Michael and Sawyer are left on what is left on the raft. They argue and nearly get eaten by a shark. Jin is no where in sight; Meanwhile, what happened to Locke and Kate when they went into the hatch is revealed.
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.”
Disturbing memories from Hurley's past cause him to struggle with a task he's assigned inside the hatch to watch over the food storage locker. Meanwhile Sawyer, Michael and Jin discover the identities of their captors whom are what's left of a group of two dozen Flight 815 survivors from the tail end of the plane led by the tough minded Ana-Lucia Cortez who insists they walk to a more secure location. Claire uncovers a shocking piece of information about the fate of the raft when the message bottled washes ashore.
A desperate and growingly insane 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, the tail crash survivors, to take them to their camp. But they are delayed when Jin and the hulking Mr. Eko are forced to go into the jungle to look for Michael before the dreaded “others” find him first. Back at the beach camp, Sun frantically searches for her missing wedding ring which triggers flashbacks to Sun and Jin's past showing how they met for the first time in early …
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, Ana-Lucia, Mr. Eko, Bernard, Libby, and flight attendant Cindy. Meanwhile, Shannon is once again haunted by visions of Walt, but she cannot convince a skeptic Sayid that her visions are real. More of Shannon's background story shows her difficult relationship with her late half-brother Boone and further detailing how her step-mother financially cut her off after the death of their father. Also, Charlie becomes jealous of …
48 days ago, the tail section of Flight 815 crashes. The survivors struggle to live when some other people on the island continue to kidnap some of them.
Tempers flare when Ana Lucia and her group stumble upon Sayid and the other castaways.
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.
When Claire comments to Mr. Eko about the Virgin Mary statue which belongs to Charlie, he asks to see it, breaks it open, and exposes Charlie's secret to Claire. Mr. Eko makes Charlie show him the place where he found the crashed plane, while his past in Nigeria is presented in flashback. John Locke teaches Michael how to shoot a rifle, and Michael uses the computer to contact someone he believes to be Walt. Claire does not want Charlie to live close to her and her son any longer.
Jack, Locke and Sawyer follow Michael who left to look for his son. They meet “the others”. More is shown about Jack's back-story.
When Charlie's vividly surreal dreams lead him to believe Claire's baby, Aaron, is in danger, Locke suspects Charlie may be using drugs again. More of Charlie's background story shows his difficult relationship with his heroin addicted brother. Meanwhile, Sawyer encourages Hurley to act on his attraction to Libby.
Survivors fear that “The Others” may have returned when Sun is injured during a failed kidnapping attempt. Meanwhile, Sawyer is an amused, but highly interested, bystander when tension escalates between Jack, Locke, Kate and Ana Lucia over control of the hatch computer, and the storage of the weapons.
The mysterious French woman, Danielle Rousseau returns to lead Sayid to a mysterious captive who claims he crashed on the island. Meanwhile, Sawyer recruits Hurley to help him find another island animal that is harassing him: a loud tree frog.
When Claire's baby falls ill, she becomes determined to find out what happened to her to regain her memory during her captivity with the Others, triggering flashbacks to her experience among the Others, and her ordeals concerning her baby. Also, Mr. Eko learns about Henry Gale and asks Jack and Loche to give him a meeting with their captive.
When Sun comes to the realization that she might be pregnant, she struggles on whether to tell Jin about the situation. After no success from Jack or Sayid, Ana-Lucia is called in by Locke to interrogate the prisoner, Henry Gale, to get more information out of him about how he arrived on the island. Ana-Lucia, Sayid, and Charlie then set out into the jungle to try and confirm Henry's story.
When the hatch suddenly takes on a life of its own, Locke is trapped alone in the bunker and is forced to enlist the help of an unlikely ally: the captive Henry Gale to try to free him. Meanwhile, Jack faces off against Sawyer in a series of card games for supplies. Also, Ana Lucia, Sayid and Charlie find out the truth about Henry in the jungle.
Hurley begins to think the island is affecting him in a very strange way, so Libby attempts to offer him support. Hurley also recalls his past in a mental hospital with his friend Dave. Meanwhile, the prisoner calling himself Henry Gale offers new information about the Hatch, which severely shakes Locke's sense of purpose.
Bernard tries to convince the survivors to build a S.O.S. signal with rocks on the sand, hoping to be seen by a satellite or an airplane. His first encounter with Rose, who was terminal, and their romance, are disclosed through flashbacks. Bernard never gives up searching for the cure of Rose before crashing the island. Meanwhile, Jack invites Kate to join him in the woods to propose to “The Others” a trade between Henry and Walt. John Locke is intrigued with the words of Henry about the unnecessary use of the computer. Is Henry playing him for a fool? Elsewhere, …
Jack and Kate bring an exhausted Michael back to camp where he has news about “The Others”. Meanwhile, Ana Lucia attempts to get the prisoner, Henry Gale to confess to being a spy for the Others, and he attempts to kill her. Also, 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, Sawyer, and Kate struggle to cope with the horrific situation in the hatch following the escape of “Other” Henry Gale, and of the shooting deaths of Ana-Lucia and Libby, unaware that it was Michael who is responsible.
Michael's whereabouts during his 13 days in captivity in the “Others” camp are detailed while in the present, he tries to convince Jack to help him mount a search party for his son Walt still being held captive. Meanwhile, Locke struggles with a choice whether or not to abandon the hatch.
After discovering a sailboat just offshore containing former hatch oversee Desmond, 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.