- "Pilot (Part 1)"
During a routine trip from Sydney, Australia, to Los Angeles, Oceanic Flight 815 is blown off course and crashes on a remote, deserted island. Convinced that rescue is coming soon, the surviving passengers set up camp on the beach and try to make the most of what they think will only be a short time on the island. One of the 48 survivors, Dr. Jack Shephard, suggests that they find the transceiver in the front of the plane so they can radio for help. But when a terrifying howl comes from the jungle, it becomes apparent that this is no ordinary island.
- "Pilot (Part 2)"
The discovery of a transceiver among the plane's wreckage and the thought that rescue could be imminent temporarily raises the castaways' spirits. And the island's mysteries continue to baffle with the discovery of handcuffs, a gun and an animal that shouldn't be able to survive in a tropical climate.
- "Tabula Rasa"
Jack and Hurley discover an alarming secret about Kate, as the marshal's life hangs in the balance. Meanwhile Kate, Charlie, Sawyer, Sayid, Boone and Shannon ponder the island's mysteries they've uncovered and worry that telling the other survivors will cause panic, and Locke's befriending of Walt disturbs Michael.
Survivors are jolted awake in the middle of the night when wild island beasts invade the beach encampment. Kate and Michael join the mysterious Locke on a hunt for food - and a shocking secret about Locke is revealed. Meanwhile, some survivors are horrified by Jack's plan for the dead bodies still scattered among the wreckage, and Jack sees someone in the jungle who might not have been on the plane.
- "White Rabbit"
Jack is near 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, the pregnant Claire's health takes a bad turn, and a thief may have stolen the last bottles of water.
- "House of the Rising Sun"
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.
- "The Moth"
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.
- "Confidence Man"
When Shannon suffers an asthma attack, Jack and Sayid realize brutality might be the only way to convince Sawyer to relinquish the life-saving medicine he's hoarding. Meanwhile, Sun struggles to decide if she'll obey husband Jin's orders to stay out of others' affairs, and Kate uncovers some shocking secrets about Sawyer.
Sayid's life is placed in grave danger after he stumbles upon the source of the mysterious French transmission. Meanwhile, Hurley has a ridiculous plan to make life on the island a little more civilized - and it just might work.
- "Raised by Another"
Jack, Kate and Charlie wonder if Claire's disturbing nightmares might be coming true to threaten her life and the life of her unborn child, and a missing castaway returns with frightening news about what lies just beyond the mountains.
- "All the Best Cowboys Have Daddy Issues"
Survivors wonder why Charlie and the pregnant Claire have been abducted - and by whom - and a search party ventures into the treacherous jungle to try to find and rescue the missing duo. Meanwhile, inner-demons about his father resurface for Jack, and Boone and Locke discover another island mystery.
- "Whatever the Case May Be"
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 disappearance.
- "Hearts and Minds"
When Locke learns that Boone wants to tell their "secret" to Shannon, Shannon's life is placed in sudden peril, and the shocking truth about her past with Boone is revealed. Meanwhile, Kate is puzzled by Sun's mysterious behavior, and a hungry Hurley must repay a debt to Jin.
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.
After the missing Claire returns with no recollection of what has happened since before the doomed flight of Oceanic 815, Jack and Locke formulate a plan of defense against her kidnapper, the mysterious Ethan, who threatens to kill off the other survivors unless Claire is returned to him.
Kate and Sawyer divulge dark secrets to each other while tracking a renegade boar that Sawyer swears is purposely harassing him. Meanwhile, Hurley and Sayid worry that Charlie is losing it after his brush with death, and a shocking, prior connection between Sawyer and Jack is revealed.
- "...In Translation"
When the raft the survivors have been building mysteriously burns down, Michael is convinced that Jin is responsible for the sabotage, which only further escalates their rivalry. Meanwhile, Sun stuns her fellow survivors with a surprising revelation, and Boone gives Sayid a warning about Shannon.
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. Meanwhile, Locke asks Claire to help build a mysterious item.
- "Deus Ex Machina"
Locke begins to suffer physical difficulties as he and Boone try to find a way into the hatch; Jack is reluctant to offer assistance when Sawyer begins to experience excruciating headaches.
- "Do No Harm"
Claire goes into labor while a helpless Charlie goes into panic mode. Meanwhile Locke is missing, Jack tends to a wounded survivor and Sayid presents Shannon with a romantic surprise
- "The Greater Good"
After burying one of their own, tempers flare as the castaways' suspicions of each other grow -- and an unlikely survivor vows revenge. Meanwhile, Claire and Charlie struggle to calm her newborn.
- "Born to Run"
Jack suspects foul play when Michael becomes violently ill while building the raft. Meanwhile a secret from Kate's past is revealed, the mysterious hatch is shown to a few of the survivors, and Walt gives Locke a warning.
- "Exodus (Part 1)"
The French woman -- Rousseau -- shocks the survivors by showing up with a dire warning about "the Others." Meanwhile, Michael and Jin ready the raft for sailing.
- "Exodus (Part 2)"
As the castaways brace themselves for an attack, Claire's baby is kidnapped, leading Charlie and Sayid on a dangerous chase into the jungle. While the threat of the Others bears down on the castaways, the raft crew continues their flight from the island - but when the hope of rescue appears on the horizon, they will soon learn that appearances can be deceiving. Charlie and Sayid stumble into a trap as they race to confront the kidnapper. Jack and Locke argue as they prepare to blow open the hatch. The raft crew is overjoyed to be dicrovered by a passing ship, but their elation is short-lived when they realise things are not what they appear. The hatch is opened, and what is inside it stuns the survivors.