Genre: Mystery

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.