Season synopsis
Contains spoilers for this season and earlier seasons.
The survivors enter the hatch and find Desmond Hume, who has been living in the Swan station and entering a code into its computer every 108 minutes. An orientation film identifies the station as part of the Dharma Initiative and says the routine prevents a dangerous buildup after an earlier incident. When the raft wrecks, Michael and Sawyer return to the island with Jin and encounter survivors from the plane's tail section, including Ana Lucia, Mr. Eko and Bernard. Their reunion brings a second camp, new losses and a growing conflict with the Others.
The Swan's supplies and weapons intensify disputes at the beach, while Locke begins to doubt the button and Jack prepares for an attack. Rousseau captures a man calling himself Henry Gale, and Sayid questions him; his evasions sharpen suspicion about the Others. Michael uses the hatch computer to contact someone he believes is Walt, then leaves camp to search for his son. Claire, Kate and Rousseau revisit the place where Claire was held, and the survivors learn that the Others have taken children before.
While captive, Michael agrees to lead Jack, Kate, Sawyer and Hurley to the Others in exchange for Walt; the bargain also requires Henry's release. Back at camp, Michael kills Ana Lucia and Libby, then releases Henry to carry out the deal. The four are captured, while Michael and Walt leave by boat and Hurley is sent back with a warning. At the Swan, Locke convinces Desmond to let the countdown reach zero; Desmond realizes the button is real and turns the station's failsafe key as an electromagnetic surge envelops the island. A distant research station detects the anomaly and alerts Penny.