This is the description of a role-playing game (originally run in 1994) which wandered in time, following the lives of four immortal characters from 1100 A.D. to the present.
As an RPG, the game had a number of unusual features. It was diceless, using a variant of the Theatrix system. It was completely troupe-style, in that the task of GMing would change with each session. It was also non-linear, in that each adventure took place decades or centuries apart, jumping backwards and forwards in time.
The campaign had the same wrap-around story: The four immortals had met in the house of Odysseus (a PC) in 1994. There they exchanged stories about their past. In each story, one PC was absent -- that is who the other PCs were telling the story to, and the player of the absent PC acts as GM.