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.

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.