Doom: The Lost Episode is an unofficial fifth episode (complete with intermission screen!) released for Ultimate Doom in 2009, requiring either ZDoom or Eternity to run. Headed by Xaser with additional credit to Skunk, Wills, Nuxius and SnowKate709, it aimed to collect unused Doom Alpha maps with maps exclusive to the various console versions of Doom and retool them to create a strange but excellent adventure (link to development thread here). For those interested the in narrative justifications Doom authors provide for their unholy concoctions, the story is quite simple. Crammed right in between Doomguy avenging the death of his pet rabbit and his arduous campaign to rid Earth itself of Hellspawn, the action finds our protagonist teleported into a fragmented dimension as a last-ditch attempt to distance Doomguy from the campaign of Evil. You'll have to fight your way through to the architects of the false reality to return to your own.
