You go to see the head of the drugs mafia at the prison and try to reason with him and persuade him to stop making your life a misery. You tell him you only found the money and took it to the police, you didn't know it was mafia money, and you had no intention of stealing it from them.
After you finish, you realise you haven't got a chance. The mafia boss just looks at you like you were something the cat had brought in, and signals to his most brutal thug, who comes over and kicks you all the way back to your cell. You just manage to close the door to your cell before he can get into it too.
Learn karate from a prison library book
Go to prison director and plead with him for protection
Try to convince the prison doctor that you are sick