Save the game after the first murder occurs. The game will be in real time and Gabriel can wander around, speaking to people, or spy on suspects for five minutes. Reload the saved game to take Gabriel on another route and learn different things about the case.
Press SHIFT + CTRL + ~ to display the console window. Type extract, press SPACE, then press ENTER. A file named "!!!Readme.txt" will be created in the game directory. Read the file on how to activate the different hidden features in the game. These include the activation of various secrets, extraction of multimedia files,and the creation of places and animations. To activate all the Easter Eggs, type Tippe: SetFlag("egg") at the console window.
Find the bookstore window that has the book on the Holy Grail. Look in the window next to the door to see Jane Jensen, the woman that developed the Gabriel Knight series of games. Also, examine the book that Gabriel authored about the Voodoo Murders. Gabriel will say "Wow, isn't he some famous author or something?".