The survivors must deal with two outcomes of the detonation of a nuclear bomb on the island in the 1970s. While the on-island story continues, "flash sideways" show a second timeline, in which Flight 815 never crashes. By the moving finale, not every piece to the six-year puzzle fits neatly into place, but series die-hards are hard-pressed to leave without an emotional appreciation for the exhilarating ride.
