In a realm, but a sliver of reality away from our own, there lived a race of people who drew strength from the written works of others. Not so different from humans, they lived, they breathed, they worked, and they played. For a time all was well.
The first ripples of discord spread upon the arrest and banishment of Doctor Balyne. A scientist who had long served the community, he shocked all when he announced the results of his latest experiment - a trans-dimensional portal known simply as "The Jump". The other scientists were thrown into an uproar. The Realm of Literacy had always survived in a delicate state. To allow crossings into other dimensions was seen as radical and dangerous. Balyne himself refused to acknowledge the potential harm which his invention could create and the investigations which followed served only to convince him that his former colleagues were too suspicious and narrow-minded to fully appreciate The Jump. When he refused to dismantle the portal, his sentence was pronounced - he was to become a guinea pig for it, thrown in with no supplies or knowledge of where he would be sent. It was little more than a death sentence, yet Balyne was all too glad to test his invention. He was sent through willingly and never seen again.
While all of this was shocking to most and even fascinating to the younger people, the entire event might very well have been forgotten if a new trouble had not set in nearly a year after the doctor's departure - the Mary Sue virus. Named for the first character diagnosed with it, the disease infected literary characters, warping them and, by effect, the rest of the story. While original works were not immune to it, the worst outbreaks were found in works of fan fiction, usually through original characters born with it. Through these original characters, the canon characters would become infected as well. The virus left the works of literature twisted and hollow and the citizens of the Realm were unable to draw power from them.
While many felt that all hope was lost, there were still those who did not give up. It was decided that the remaining scientists would study this strange disease and find a way to destroy it and free the infected from its grasp. At the same time however, a more direct approach was needed for the infectious original characters. Those born with the Mary Sue virus had almost no hope of redemption. The best that could be hoped for would be to train soldiers to enter the stories and destroy the infected (referred to henceforth as "Mary Sues" and "Marty Stues") , containing the damage and saving canon characters from the disease.
And thus, the Management Assemblage for Removal of Yawing Special Unit Extermination was born, training the next generation in the art of Mary Sue extermination. Upon completion of training, the Agents are sent through The Jump (extensively studied and modified) to a work of literature in which they must find and destroy any and all Mary Sues. Guided by their Seconds and armed with powerful technology, the Agents face the risk of death or infection themselves...