Ah, the storyline is where you start of course. YOu say you want to make a story for TT. Maybe you could have something to do with Aztecs and how they killed people for their gods. Perhaps you could start the story based on a French man, depending if this is historically based you could pretend that the French and Spanish are in a war, or maybe not. Somehow though this French man travels to Spain and somehow gets trapped there. Anyway then the conquestadors might decide to head to the new world and Frenchy gets brought along with them. Perhaps they then decide to have a shipwreck and are stuck there in Mexico and the French man is seperated from the others. Perhaps of course. He could have been brought along as a crew member or perhaps a slave. Maybe he travels there by other means but sometime in the story he sees people (Conquies or perhaps Mayans or other Aztecs) being sacraficed. You could accomplish this by having the player on a cliff ledge and viewing a line of prisoners being killed as they walk to an Aztec castle inbetween two monks they die using the kill trigger. By the end of the scenario the Frenchman might eventually find his way back to Europe and the story has a happy ending.
You could play with that idea and do whatever you like to it. You can do almost anything with triggers : ) I know though it take some time and may cause a few headaces but you will probably be pleased with the idea.