Beyond Castle Wolfenstein is a 1984 action-adventure game developed and published by Muse Software. A direct sequel to Castle Wolfenstein, it is the second game in the Wolfenstein series. Castle Wolfenstein was written solely by Silas Warner for the Apple II, while the sequel was developed simultaneously for the Apple II and Commodore 64 by Warner, Eric Ace, and Frank Svoboda III. It was quickly ported to the Atari 8-bit computers and MS-DOS.