Contains spoilers for this episode and earlier episodes.
An alarm wakes a man inside a furnished underground compound. He enters something into a computer, then exercises, showers and prepares breakfast before the blast opening the hatch interrupts his routine. Above ground, Jack wants the survivors to wait until daylight before exploring, but Locke insists on entering. Jack returns to the caves to reassure the frightened group. Locke gathers a cable and heads back to the hatch; Kate follows and descends first. A bright light shines up the shaft, and she disappears from his view. Jack subsequently follows them. Elsewhere, Shannon searches for Vincent and sees a drenched Walt speaking strangely in the jungle, though the others do not accept her account.
Flashbacks show Jack treating Sarah after a serious car accident. He saves her life but tells her that her spinal injury may prevent her from walking again. Christian criticizes his son's lack of hope, and Jack promises Sarah that he will fix her. After the operation, Jack believes he has failed. While running stadium steps, he meets Desmond, who encourages him to consider the possibility of a miracle. Sarah subsequently discovers that she can move her feet. On the island, Jack descends into the compound and finds equipment, a mural and a powerful magnetic pull. Locke appears under a gunman's control. When the armed man steps forward, Jack recognizes Desmond from the stadium.