I am a movie director and I just received the following movie plot. Could you help me answer this question? If not, let me know by writing "Not answerable". Plot title: Tron: Legacy Movie plot: 1989: Kevin Flynn (Jeff Bridges), now CEO of ENCOM, tells his seven year-old son, Sam (Owen Best), about his adventures in the Grid, a completely digital world within the Tron computer system that Flynn created. Flynn explains to Sam that, with his counterpart Clu (Jeff Bridges, body performance; John Reardon) - the second of a Codified Likeness Utility modeled after Flynn - and the security program Tron (Bruce Boxleitner), he discovered something amazing within the Grid; a miracle. Sam asks what it is but Flynn holds the story for next time before putting Sam to bed and going to work. A series of newspaper articles and television reports follow announcing the mysterious disappearance of Kevin Flynn after that night. Since the passing of Sam's mother (Amy Esterle) several years prior, Flynn's absence leaves him effectively orphaned and puts ENCOM's future in a state of jeopardy. Sam is left to stay with his paternal grandparents (Donnelly Rhodes and Belinda Montgomery), questioning the nature of his father's disappearance.20 years later, Sam (Garrett Hedlund) rides his motorcycle through the night streets towards ENCOM tower. He hacks into the building and evades security cameras as he makes his way upstairs. Meanwhile, a board meeting is being held where Richard Mackey (Jeffrey Nordling) presents the new OS-12, a secure operating system. When Alan Bradley (Bruce Boxleitner) inquires about improvements to the system, given the high prices already charged, young Edward Dillinger II (Cillian Murphy: uncredited) says that the idea of sharing software for free disappeared with Kevin Flynn. Sam breaks into the control room and swaps out the OS-12 master file so that when Mackey attempts to run it, all he sees is a repetitive video of Sam's dog Marv (a Boston terrier). Sam smirks as he passes the boardroom, followed closely by a security guard (Dan Joffre). When Mackey angrily asks where the master file is, Bradley announces that it's on the web.The security guard, Ernie, chases Sam onto the rooftops where Sam... My question: What is the master key to the Grid?
Answer:
Flynn's "identity disc"