From Wikipedia: Fairlight: A Trail of Darkness is an isometric 3D arcade adventure game released by The Edge in 1986 for the Sinclair Spectrum and Commodore 64. It is the sequel to Fairlight. The game is very similar to its predecessor, though it is larger with more locations to explore.
Isvar successfully retrieved the Book of Light in Fairlight, but was then tricked into delivering it to the Dark Lord, who is now using it to further torment the land of Fairlight. Isvar must penetrate the Dark Tower and recover the book so that it may be taken to its rightful owner.
Source: Wikipedia, "http://en.wikipedia.org/wiki/Fairlight_II_%28video_game%29," available under the CC-BY-SA License.