From the file's introduction
This adventure, which begins on a coastal shoreline in Avalon, allows the characters to witness the fall of one of the greatest legends in Théah – the powerful Derwyddon. Unlike other 7th Sea adventures, this one has a definite beginning and end. The heroes are powerless to change the outcome of the hardpoints which will occur whether they persevere through the adventure or not as the story involves events in the official timeline. Even if the players manage to find a way around the tragic end of this story, it will occur upon another day. Tragedy can be fought and postponed, but it is inevitable. This is one of those times when a hero can only bear witness to that end.
This does not mean that the heroes themselves are powerless. While they cannot alter Derwyddon's fate, they can forge a relationship with several important Sidhe nobles and gain powerful artifacts to use in other situations. The Sidhe in this adventure more power than any human could fathom, but are hindered, as are others of their kind, by a lack of understanding of what it means to be human. The heroes might be able to change all of that.