After their plane, Oceanic Air flight 815, tore apart whilst thousands of miles off course, the survivors find themselves on a mysterious deserted island where they soon find out they are not alone.
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, 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.
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.
The celebration of Jack’s return is cut short when he arrives at the beach with an Other, Juliet, whose flashbacks pick up from where they left off, showing us how she got onto the island and became an other. Meanwhile, Claire is threatened by a strange illness.
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 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.
Kate and Juliet are stranded in the jungle after Kate learns that there is a traitor in the survivor’s midst. Meanwhile, Sawyer’s poor attitude and selfish ways towards the beach community may earn him a vote of banishment if he doesn’t have a change of heart.
When Locke learns that Boone wants to share their “secret” with Shannon, Locke decides to teach him a lesson. Boone and Shannon’s dark past is revealed in a shocking backstory that recalls their relationship right before the plane crash. Kate, who has become a confidante to the soft-spoken Sun, is puzzled by Sun’s mysterious behavior. 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.
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.
As the truth about Sun’s kidnapping by “the Others” comes to her attention, Hurley becomes suspicious of Sawyer’s attempt to reveal the mystery behind two fellow survivors, Nikki and Paulo. Through series of flashbacks we will discover what Nikki and Paulo were doing before the crash and how they survived 65 days on the island.
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.
