The Cookie Monster

"The Cookie Monster" is a 2004 Hugo Award-winning novella by Vernor Vinge. The story begins following the first day of Dixie Mae Leigh's job as a customer support employee at a fictional company called Lotsatech. She receives an insulting and mysterious email and, in a fit of rage, decides to find out who sent it. She and a fellow employee Victor search the Lotsatech campus looking for the author of the email, following clues in the email header. They meet up with Ellen, a grad student in computer science, who decides to try and help Dixie Mae. While they talk, several mysteries arise and convince them that the email may be a kind of warning about something going on at Lotsatech involving a professor named Gerry Riech, who seems to be involved in all the projects on the campus. Ellen finds another clue in the email leading the three to another building where, to their utter astonishment, a second Ellen appears. The only explanation of this is that they are being simulated by a... full article at wikipedia