On Jacob's orders, Hurley leads Jack to a lighthouse. Meanwhile, Claire questions an Other she has captured while tending to an injured Jin. In the flash sideways, Jack is a single father trying to bond with his son.

The survivors split into two groups; one led by Sawyer, the other by the Man in Black. Sawyer's group travels to Hydra Island, where they are captured by Widmore's crew after Sun and Jin are reunited. In the flash sideways, the passengers of Oceanic 815 continue to cross paths with each other.

Ben finally takes his revenge on Widmore after accepting the Man in Black's request for assistance. Jacob explains the purpose of the candidates, and Jack volunteers to take his place. The search for Desmond reveals that he has been rescued and the Man in Black plans to use him to destroy the island. In the flash sideways, each person ends up on their way to a concert.

For different reasons, Jack and the Man in Black both use Desmond to extinguish the light at the heart of the island. The island starts disintegrating, but The Man in Black is also made mortal. Still desperate to escape, The Man in Black fights Jack and mortally wounds him, but with help from Kate, Jack kills him. Realizing his destiny, Jack sacrifices himself to relight the heart of the island, so his friends can escape on the Ajira plane. Hurley takes Jack's place as protector of the island and makes Ben the new advisor. The flash sideways is revealed to be a type of limbo, or holding pattern, for the main characters, where they reside until accepting their life and death, and are then able to "let go" and "move on" together.