The Fourth Protocol

This interactive fiction computer game is based on the bestselling Cold War spy novel by Frederick Forsyth released in 1984 by Hutchinson publishing. As the novel's hero John Preston, you have been appointed head of the CI(A), an agency of the British Secret Intelligence Service. You uncover a plot, named AURORA, to take power in the Soviet Union hatched by a secret faction of high-level minds. In order to stop their plan you read a lot of info found in Top Secret folders, set wiretaps, monitor and interrogate suspects and informants, and gather facts and clues.

The game has three main sections - The NATO Documents, The Bomb and The SAS Assault. A secret code must be gained in order to proceed from one to the next. Unique icon-based graphics provide the means to conduct your investigation though they're not mouse-clickable (you have to browse the icons using the keyboard). Plot twists and developments happen during the game and are communicated to you with text-only descriptions.