It's very open-ended. I give some options for the players, but for the most part, they decide what to do, and I base the next major event off of that. I have several major plot points I plan to introduce over the course of the RP, but they're flexible enough that I can fit them to the RP as it changes. I don't want to incorporate a chapter system, because that would create too linear a system. Hope I answered your question >.>