Out of the blackness, the first thing Jack (Matthew Fox) senses is pain. Then burning sun. A bamboo forest. Smoke. Screams. With a rush comes the horrible awareness that the plane he was on tore apart in mid-air and crashed on a Pacific island. From there it's a blur, as his doctor's instinct kicks in: people need his help.

The discovery of a transceiver among the plane's wreckage and the thought that rescue could be imminent temporarily raises the castaways' spirits. 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.

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. 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 as 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.

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, the pregnant Claire's health takes a bad turn, and a thief may have stolen the last bottles of water.

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. Locke discovers Charlie's secret.