Itinérance (the itinerants, or the roamers/homeless) is a caravan of airships. These 18 balloons (dirigibles/blimps) travel the world of Ecryme, from city to city, by flying over the ecryme and the bridges/railroads that connect the cities.
The caravan airships engage in a perpetual wandering linking major cities of the known world. Each trip lasts one year, during which the thousands of people in the caravan practice their arts, conduct research, establish diplomatic and trade relations and pursue goals that are less public.
The book is divided into two parts. The first presents the caravan, its history, its operation (technical and sociological) and the cyclical journey it completes each year. Every airship is then presented in detail, including its "visible features" (the things that everyone can know) and its innermost (hidden) parts.
The second part of the book presents five scenarios. They are independent and can each be played in a long night-time session. Surprisingly enough, the scenarios are not all for Itinérance. The first three take place in the city of Eole and require that supplement to be played. The fourth, begins at Eole but presents the players with an opportunity to be accepted on the caravan. Finally, the last part for Itinérance itself.