Sun comes to the realization that she might be pregnant. She struggles on whether to tell Jin about the situation. Meanwhile, with no success from Jack or Sayid, Ana-Lucia is called in by Locke to interrogate the new prisoner Henry Gale to get more information out of him about the balloon that he and his wife supposedly landed on the island with.

A mysterious illness that baby Aaron suddenly contracts sends a desperate Claire, Kate and French woman Danielle to return to the same area where Claire was initially kidnapped. It is there where she believes she can find a cure for Aaron’s illness. In the meantime, Jack and Locke are doing their best to keep their prisoner a secret from the rest of the survivors on the island.

After Sun is attacked, some of the survivors begin to think that one of the “other survivors” might be one of “The Others.” When French woman Danielle 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 breach of the survivors’ trust and blackmails him into helping track an elusive island creature that won’t leave Sawyer alone.

Some of the island survivors fear that “The Others” may have returned when Sun is greatly injured during a failed kidnapping attempt at her plant garden. Also, the trust barrier becomes very thin between Locke and Jack in terms of locking up the guns and being kept safe. Meanwhile, Sawyer is an amused but highly interested bystander when tension escalates between Jack, Locke, Kate and Ana Lucia. When Jack purposely takes Sawyer’s medication from him he pushes more in favor of helping Locke. Lastly, flashbacks reveal more of Sawyer’s con artist past.

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.

Jack, Locke and Sawyer follow after 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.”

This episode will shed more light on why Eko took a mysterious 40-day vow of silence, and possibly information on his stick. Also, Claire begins to lose faith in Charlie after Eko begins to question him about the Virgin Mary statue, and Kate gives the recovering Sawyer a much-needed haircut.

As Kate’s backstory continues, her original crime is revealed. She thinks something is haunting her through Sawyer. Locke and Eko make an interesting discovery about the film, and Michael has a mysterious encounter with the computer.

Violence erupts when Ana Lucia and her group stumble upon Sayid and the other castaways on the island. Ana Lucia holds Sayid captive. Kate and Jack care for Sawyer when Mr. Eko brings him back to the camp himself. Flashbacks reveal Ana Lucia’s troubled life as a cop.

The harrowing first 48 days in the lives of the tail section survivors are revealed. Flashbacks reveal the point of view of Ana-Lucia, Mr. Eko, Bernard and Libby and other survivors as they landed on the other side of the island on the beach. As the days progress danger hits their camp as well when “The Others” start taking people against their will. As the survivors race inland, trying to stay a step ahead of The Others, they realize that someone among them wasn’t on Flight 815.

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.

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. In flashbacks this episode reveals more of Jin’s life before ending up on the island.

Hurley struggles with an assigned task inside the hatch as he flashbacks to disturbing memories in his life before the crash. Meanwhile, Sawyer, Michael and Jin learn the identities of their captors on the island. Claire uncovers a startling piece of information about the fate of the raft.

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.” Flashbacks reveals more of Locke’s past in this episode as well as the introduction of Helen (guest star Katey Segal) who shakes things up even more with her revealing personality and past.

With the abduction of Walt fresh on their minds, their raft destroyed, and Jin missing, Michael and Sawyer fight for their lives in the middle of nowhere in the ocean and discover a new predator in the roiling sea. Meanwhile on land, Locke must descend into the hatch when Kate goes missing inside. Also, Jack isn’t too far behind Locke as he decides to go into the hatch as well later on. Lastly, flashbacks reveal more of Michael’s troubled relationship with ex-lover Susan and their baby son Walt as they fight over custody for Walt and Michael must let go.

Jack, Locke and Kate explore the mysterious hatch but Jack decides to wait before going down into the hatch. Kate and Locke aren’t so patient. When Shannon chases after Vincent the dog, she encounters a familiar face in the jungle.

The castaways on the raft run into unexpected trouble. Meanwhile, the remaining islanders attempt to blow open the hatch. Flashbacks continue to show the survivor’s final moments before boarding their fateful flight.

The French woman-Danielle Rousseau-shocks the survivors by showing up to the camp with a dire warning about “the Others” who are on the island, and the black smoke that precedes them. Meanwhile, Michael and Jin ready the raft for sailing. In flashbacks, we see the survivors final moments before they boarded their fateful flight.

Jack suspects foul play when Michael becomes violently ill while building the raft. The suspects include Sawyer and Kate, who compete for the last seat on the raft and do anything possible to prevent each other from getting it. Meanwhile, a secret from Kate’s past is revealed to the other survivors on the island.

After another funeral, tempers rise as the survivors’ suspicions of each other grow, and an unlikely survivor vows revenge. The events that landed Sayid on Flight 815 play out as he engages Locke in a psychological game of cat and mouse to uncover the truth about the mishap that claimed Boone’s life.

Jack tends to a severely wounded Boone after Locke returns him to the caves. In the confusion, Locke slips away to deal with his guilt over the crisis. Meanwhile, Claire unexpectedly goes into labor while deep in the forest.

Locke thinks he’s being sent a sign on how to get the hatch open, and he and Boone venture inland. Jack is reluctant to offer assistance when Sawyer begins to experience excruciating headaches and needs glasses.

When Hurley becomes obsessed with the French woman and heads into the jungle to find her, Jack, Sayid and Charlie have no choice but to follow. Hurley flashes back to the hugely life-altering experience he had before boarding the plane.

When the raft the survivors have been building mysteriously burns down, Michael is convinced that Jin is responsible for the sabotage, which only serves to escalate their rivalry. Meanwhile, Sun stuns her fellow survivors with a surprising revelation, and Boone gives Sayid a warning about his step-sister Shannon. Lastly, more details of Jin and Sun’s troubled marriage are revealed through flashbacks.

Kate and Sawyer divulge dark secrets to each other while tracking a renegade boar that Sawyer swears is purposely harassing him. Hurley and Sayid worry that Charlie is losing it after facing a brush with death and killing Ethan with 6 bullets to the chest. A shocking prior connection between Sawyer and Jack is revealed in a flashback which shows Sawyer meeting Jack’s father in a bar. Robert Patrick (“Terminator 2: Judgment Day,” “The X-File”) guest stars.

After the missing Claire returns with no recollection of what has happened since before she boarded the doomed Oceanic flight 815, Jack and Locke formulate a plan of defense against her kidnapper, the mysterious Ethan (guest-star William Mapother), who threatens to kill off the other survivors one by one unless Claire is returned to him. Meanwhile, the disappointment Charlie feels when Claire does not remember him triggers recollections of a woman he had let down in the past.

Violence ensues and a mysterious island beast makes a re-appearance when Michael and Locke clash over Walt’s upbringing. Meanwhile, Charlie is tempted to read the missing Claire’s diary, and Sayid enlists Shannon to help decipher the French woman’s map.

When Locke learns that Boone wants to share their “secret” with Shannon, Locke decides to teach him a lesson. This leads to Shannon’s life being placed in what seems like peril. Boone and Shannon’s dark past is revealed in a shocking backstory that recalls their relationship right before the plane crash and presages the return of the beast. Kate, who has become a confidante to the soft-spoken Sun, is puzzled by Sun’s mysterious behavior and the revelation that she can speak English. A hungry Hurley must convince Jin to share his fish by making up for offending Jin by rejecting his offer of raw fish early on, or he’ll continue to suffer digestive problems from the limited island diet.

Jack, Kate and Sawyer fight over possession of a newly discovered locked metal briefcase which might contain insights into Kate’s mysterious past. Meanwhile, Sayid asks a reluctant Shannon to translate notes he took from the French woman. A rising tide threatens to engulf the fuselage and the entire beach encampment, and Rose and a grieving Charlie tentatively bond over Claire’s baffling kidnapping.

Survivors wonder why Charlie and Claire have been abducted – and by whom – and a search party ventures into the treacherous jungle to look for the pair. Suspicions focus on Ethan Rom (guest-star William Mapother), who, it was recently discovered, was not a passenger on the doomed flight. Jack battles inner demons relating to his father, while Boone and Locke discover another island mystery.

Claire has a horribly realistic nightmare about her new baby being harmed or kidnapped. Flashbacks reveal Claire’s backstory: the former boyfriend who got her pregnant, then abandoned her, and the psychic who convinced her to take the ill-fated flight that landed her on the island. Hurley is shocked and confused when he discovers that Ethan Rom (guest-star William Mapother), another plane crash survivor, does not appear on the flight manifest.

Sayid’s life is placed in grave danger after he stumbles upon the source of the mysterious French transmission, the woman Danielle Rousseau (guest-star Mira Furlan). She was on the distress call and is found alive. Meanwhile, Hurley has a ridiculous plan to make life on the island a little more civilized. The plan involves golf clubs he finds in the debris, and it looks like it just might work. Lastly, we flash back to Sayid’s childhood friend Nadia as well as his participation in hostage situations in Iraq.

Shannon’s inhaler runs out and Boone believes Sawyer has the remaining three in his stash. When Sawyer refuses to give them up, Jack and Sayid resort to torturing Sawyer until he agrees to reveal the location of the inhalers. In flashback we hear Sawyer’s story and find he is not who he says he is.

Charlie begins a painful journey of withdrawal from drugs, surprisingly aided by Locke, whose true motive for helping Charlie is a mystery. Meanwhile, survivors struggle to find and free Jack when he’s buried alive in a cave collapse, and someone might be secretly thwarting Sayid, Kate, and Boone when they enact a plan to find the source of the French transmission.

Walt and the others are shocked when Michael is brutally beaten, but only the non-English-speaking Jin and Sun know the truth behind the attack. Meanwhile Kate, Jack, Sawyer and Sayid argue about where the survivors should camp — on the beach, where they’re more likely to be seen, or in a remote inland valley where fresh water abounds; and Locke discovers Charlie’s secret.

Jack is nearly delirious from lack of sleep and struggles to overcome the haunting events that brought him to Australia and, subsequently, to the island. Meanwhile, Boone gets caught in a treacherous riptide trying to save a woman who went out swimming. A pregnant Claire’s health takes a bad turn from lack of fluids, and a thief may have stolen the last bottles of water. Veronica Hamel guest-stars as Jack’s mother, Margo.

Also, Jack flashes back at 12 years old, to find himself on the playground in an altercation with a bully, who ultimately beats him up, and later learns a life lesson from his father.

The survivors are jolted awake in the middle of the night when wild island beasts (which are wild boars) invade the beach encampment. Kate and Michael join the mysterious Locke on a hunt for food — and a shocking secret about Locke is revealed. On the hunt for food someone is injured. Meanwhile, some survivors are horrified by Jack’s plan for the dead bodies still scattered among the wreckage — he wants to burn them. Jack sees someone that’s not there, and we find out that one of the survivors was not able to walk but now he can.

Jack and Hurley discover an alarming secret about Kate, as the marshal’s life hangs in the balance and he suffers a lot of pain. Meanwhile Kate, Charlie, Sawyer, Sayid, Boone and Shannon ponder the mysteries they have begun to uncover and worry that telling the other survivors will cause panic. They decide to lie for the time being. Also, Locke’s befriending of Walt disturbs Michael, but Walt is more concerned in finding his dog. Lastly, Kate flashes back to when she was arrested by the marshal in Australia.

Having escaped the “creature” and retrieved the plane transceiver, a group of the survivors travel to higher ground so they can transmit a signal. En route, they receive a mysterious transmission and encounter another of the island’s inhabitants. Meanwhile, back at camp, Jack tends to a wounded man who reveals a secret about Kate.