The Man in Black's final fate is determined, and one survivor must make the ultimate sacrifice to save the island. Meanwhile, in another life, the ones who might have been the survivors gather for a final time.
There's No Place Like Home — Michael Giacchino
Jack has a flash of his life with Locke. Locke enters the church. Jack remembers his life on the island. He walks to the bamboo grove. Christian opens the doors to the church. Jack dies.
Ben switches off his walkie-talkie so the Man in Black can't hear it. Ben, in the flash-sideways timeline, speaks to Locke for the last time, apologizing for killing him.