Wolfenstein 3D: Third Encounter is a Macintosh port of the 60 levels from the original MS-DOS Wolfenstein 3D, published in 1994 by MacPlay. It acts as a follow-up campaign to the Second Encounter game from the same publisher. Third Encounter was originally only available as mail-order, after having purchased Second Encounter. It is part of the Mac Family line of Wolfenstein 3D ports.
In 1995, both Second and Third Encounters were published together in a retail box for the Macintosh and simply called Wolfenstein 3D (this release is sometimes known as the "Commercial Version"). This 90-level version presented the user with 7 missions: Second Encounter, followed by each of the 6 original MS-DOS missions. When this retail release was ported to the 3DO and Apple IIGS, the Second Encounter mission was renamed to Original Encounter.
See the Original Encounter article for more details on the levels and story.
This backstory is taken from the original DOS version of the game (most of the Mac Family games that have adaptations of these levels do not actually have any in-game storyline details, but only what the manual describes for the character and his motives).
Following the events of the Original Encounter and the Nocturnal Missions, B.J. is again sent into stop Hitler's new plan. This time rumors of Operation Eisenfaust. He is captured before he is able to infiltrate Castle Wolfenstein, and thrown into the castle dungeon. After defeating Hans Grosse for the second time, he ran out of the castle and hooked up with the Underground. They informed him that the rumors were true: some hideous human experiments were seen around Castle Hollehammer. He confirmed that Operation Eisenfaust was real.
He was ordered to journey there and terminate the maniacal Dr. Schabbs before his undead armies marched against humanity. Following a long battle, B.J. stood over Schabbs fat, evil, swollen putrid body, glad his mission was finally over. All his journals and equipment would be destroyed. Hopefully, humanity would finally be safe from his hordes of hideous mutants.
Yet the Nazi atrocities continued: thousands march into death camps even as the Nazi war machine falls to its knees. There was only one way to stop this madness.
After defeating Dr. Schabbs, Hitler again was forced to flee. He had escaped to the Reichstag, and hid in his titanic Reich Bunker as the Third Reich crumbled about him. B.J. was ordered again confront him, and to assassinate Hitler, and end his mad reign. After a long battle, the absolute incarnation of evil, Adolf Hilter, lie at B.J.'s feet in a pool of his own blood. His wrinkled, crimson-splattered visage still strains, a jagged-toothed rictus trying to cry out. Insane even in 'death'. B.J's lips pinched in bitter victory, he kicked his head off his remains and spit on his corpse. "Sieg heil ... huh. Sieg hell."
The Third Encounter levels correspond to the 60 levels of the MS-DOS version. They are not an exact adaptation, with high modifications in the level format, as well adapted to its own wall and items pack. Some other changes include adding the new weapons and items from Second Encounter, and changes in level structure (such as the secret pushwall maze in E2M8). This version adds Flamethrower and Rocket Launcher into the missions.
The first three episodes have the original MS-DOS bosses (Hans Grosse, Dr. Schabbs, and Adolf Hitler, respectively). The Nocturnal Missions episodes, however use some Spear of Destiny bosses: Trans Grosse, the Death Knight and a Death Knight clone alongside a Trans Grosse clone, respectively. The Death Knight drops a silver key, instead of a gold key, to support the final level of the Confrontation episode that contains two bosses.