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.

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.