The Scarecrow's Message (Batman Arkham City)

Throughout Arkham City, Batman picks up three incoming signals on a radio transmission Chanel (700,500), (500,900) and (200,500) which give out a string of letters. 

Batman hacks into the final broadcast, using the password "Scarecrow" to successfully gain access to the third message for decoding.

The letters form the message from Jonathan Crane, stating that he is alive and that he will destroy Gotham and make Batman suffer for his defeat at Arkham Asylum a year before.

The exact message reads: "I will return Batman. You will pay for what you did to me. Fear will tear Gotham City to shreds."