"LA X, Parts 1 & 2" is the two-hour premiere of the sixth and final season of the television series Lost . This episode introduces a unique narrative structure known as "flash-sideways," which depicts two parallel realities simultaneously: one where Oceanic Flight 815 never crashed and another where the survivors remain on the island in the present day after the detonation of the hydrogen bomb. Key Plot Developments "Lost" LA X: Part 1 (TV Episode 2010) - IMDb