Jack's decision to put a plan in action in order to set things right on the island is met with some strong resistance by those close to him, and Locke assigns Ben a difficult task.

Jack's decision to put a plan in action in order to set things right on the island is met with some strong resistance by those close to him, and Locke assigns Ben a difficult task.

Two outcomes of the detonation of the hydrogen bomb are presented. Flight 815 lands safely at LAX, where Kate escapes from the marshal and Jack learns that his father's body was lost in transit.

Jack, Sawyer, Kate, Miles and Hurley, struggling to save Sayid, face an ancient secret. Meanwhile, a fake Locke exits the chamber to everyone's awe.

On the island, the Man in Black attempts to recruit Sawyer in his attempt to leave the island, while an impromptu funeral is held for the real Locke. In the flash sideways, Locke is fired from his job and becomes a substitute teacher.

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.

Richard Alpert's back story is shown: In 1867, he is brought to the island on the Black Rock as a slave. He makes a deal with Jacob to be his representative in exchange for immortality. In the present day, Hurley convinces him to help the candidates replace Jacob and stop the Man in Black from leaving the Island.

Jacob and the Man in Black are revealed to be twin brothers. They are raised by a mysterious woman who is charged with protecting the island. As revenge for the murder of their adoptive mother (who killed their real mother), Jacob throws his brother into the source of electromagnetism after being made the island's guardian, which transforms the Man in Black into the smoke monster.

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.