three episodes: "Escape from Castle Wolfenstein", "Operation: Eisenfaust", and "Die, Führer, Die!" serve as the primary trilogy, with a second trilogy titled The Nocturnal Missions including "A Dark Secret", "Trail of the Madman", and "Confrontation". The protagonist is William "B.J." Blazkowicz, an American spy of Polish descent, and the game follows his efforts to destroy the Nazi regime. In "Escape", Blazkowicz has been captured while trying to find the plans for Operation Eisenfaust (Iron Fist) and imprisoned in Castle Wolfenstein, from which he must escape. "Operation: Eisenfaust" follows his discovery and thwarting of the Nazi plan to create an army of undead mutants in Castle Hollehammer, while in "Die, Führer, Die!" he infiltrates a bunker under the Reichstag, culminating in a battle with Adolf Hitler in a robotic suit equipped with four chain guns. The Nocturnal Missions form a prequel storyline dealing with German plans for chemical warfare. "A Dark Secret" deals with the initial pursuit through a weapons research facility of the scientist responsible for developing the weaponry. "Trail of the Madman" takes place in Castle Erlangen, where Blazkowicz's goal is to find the maps and plans for the chemical war. The story ends in "Confrontation", which is set in Castle Offenbach as he confronts the Nazi general behind the chemical warfare initiative. An additional episode, titled Spear of Destiny, was released as a retail game by FormGen. It follows Blazkowicz on a different prequel mission, trying to recapture the Spear of Destiny from the Nazis after it was stolen from Versailles. FormGen later developed two sequel episodes, "Return to Danger" and "Ultimate Challenge", each of which feature Blazkowicz as he fights through another Nazi base to recover the Spear of Destiny after it has been stolen again as part of a plot to build a nuclear weapon or summon demons. Development In October–December 1990, a team of employees from programming studio Softdisk calling themselves Ideas from the Deep developed the three-part video game Commander Keen in Invasion of the Vorticons, the first game in the Commander Keen series. The group, who worked at Softdisk in Shreveport, Louisiana, developing games for the Gamer's Edge video game subscription service and disk magazine, was composed of programmers John Romero and John Carmack, designer Tom Hall, artist Adrian Carmack, and manager Jay Wilbur. After the release of the game in December through shareware publisher Apogee Software, the team planned to quit Softdisk