Contains spoilers for this episode and earlier episodes.
Jack helps free Sawyer's group from Widmore's cages while the Man in Black attacks as the smoke monster. The survivors head for the Ajira plane, but explosives found aboard redirect their escape toward the submarine. Sawyer asks Jack to keep the Man in Black off it. During the rush to board, Kate is shot and Jack pushes their supposed ally into the water. Sawyer orders the submarine to dive, leaving Claire behind. Underwater, Jack discovers a timed bomb hidden in his backpack. He argues that the Man in Black needs the candidates to kill one another and urges Sawyer to leave the wires alone.
Sawyer pulls them anyway, accelerating the countdown. Sayid tells Jack that Desmond is alive in a well, then runs away with the bomb. The explosion kills Sayid and floods the submarine. Hurley takes Kate out while Jack carries the unconscious Sawyer to safety. Sun is trapped by debris, and Jin refuses to leave her; they drown together. The surviving four mourn on the beach. In the flash-sideways, Jack offers Locke surgery for his paralysis and investigates his refusal. Locke reveals that a plane he piloted crashed, injuring him and leaving his father Anthony Cooper unresponsive. Jack urges him to stop punishing himself, but Locke declines treatment. Jack also invites Claire to stay with him after they discuss their father.