- This article is about the narrative technique. For an analysis of the season 6 afterlife, see Flash sideways world.
Season 6 introduced a new narrative technique - the flash sideways. Like flashbacks and flash forwards, flash sideways intercut into episodes' main action a secondary storyline, which covered the centric characters at a different time. The series finale revealed the nature of the world the flash sideways portrayed: it showed the characters meeting after death. As such, the flash sideways are in a sense Flash-forwards.
The flash-sideways transition sound effect is characterized by a broken, stuttering version of the normal flash-forward/flashback sound, although slightly higher-pitched, almost resembling the sound coming from an airplane engine. It closely resembles the sound of the Ajira flight passing overhead - the last real sound that Jack heard before he died. The sound effect could be the actual 'sound' of Jack's transition to the flash-sideways world.
List of flash sideways episodes
- "LA X, Parts 1 & 2" - Jack, Hurley, Jin & Sun, Locke, Kate, Sawyer, Sayid, Charlie, Boone
- "What Kate Does" - Kate
- "The Substitute" - Locke
- "Lighthouse" - Jack
- "Sundown" - Sayid
- "Dr. Linus" - Ben
- "Recon" - Sawyer
- "The Package" - Jin & Sun
- "Happily Ever After" - Desmond
- "Everybody Loves Hugo" - Hurley
- "The Last Recruit" - Locke, Sawyer, Claire, Sayid, Jack, Jin & Sun
- "The Candidate" - Jack & Locke
- "What They Died For" - Jack, Desmond, Ben, Sawyer
- "The End" - Jack, Ben, Locke, Sawyer, Kate, Desmond, Hurley, Miles, Sayid, Jin & Sun, Claire, Charlie, Juliet
In "Happily Ever After", Desmond Hume transitioned between the original timeline and the flash-sideways timeline with the absence of the flash-sideways sound effect, in a similar fashion to the way in which his story transitioned between present and past in "The Constant" without the flashback/flash-forward sound effect. However, the sound effect was used at the end of the episode, when he transitioned back into the sideways timeline, indicating that this last flash was a normal flash-sideways, and not consciousness-travel, as the main body of the episode was.