Spoilers for this episode and earlier episodes of Lost.
Daniel returns to the island in 1977 after seeing the photograph of Jack, Kate and Hurley among Dharma's recruits. He challenges Jack's belief that Eloise sent them back because they were meant to be there. At the Orchid, Daniel warns Pierre Chang that drilling at the Swan will cause a disaster within hours. He reveals that Miles is Chang's adult son, but Miles refuses to support the claim and Chang dismisses the warning.
Flashbacks show Eloise directing Daniel away from music and toward science. Widmore later funds his research and visits him after experiments damage his memory. Widmore claims the island can heal him, and Eloise encourages him to join the expedition despite knowing what awaits him. In 2007, Eloise visits Penny at the hospital after Desmond is shot. Desmond survives, while an exchange outside between Eloise and Widmore reveals that Widmore is Daniel's father.
In 1977, Sawyer's group prepares to abandon Dharma, but Daniel takes Jack and Kate to find the Others. A gunfight with Radzinsky interrupts their attempt to collect weapons. Daniel explains that people are variables capable of changing events and proposes using Jughead to destroy the energy pocket before the Swan accident. He believes that would prevent Flight 815's crash. At the Others' camp, he points a gun at Richard and demands Eloise. She shoots him from behind. Daniel recognizes his mother and tells her he is her son as he dies.