The main idea is to create the best Horatio / other fanfiction. The major details are left up to you. For reference to a brilliant fanfic read. Only Love - by LucyGrissom
Calleigh allows herself to become a hostage to save a fifteen year old girl from witnessing her mother's death. In the process, the man holding her hostage beats Calleigh until she is barely conscious. The guy then forces Calleigh to call Horatio and tell him what has happened. Now Horatio must save his young friend and stop her from becoming a murder victim. Does Calleigh make it out or does she die?
I'd love to see a crossover fic with Sara and Horatio... I don't mind whether they're just friends or lovers, but I'd love to see them interact, and see H being his usual caring self.