Your father, Jack Napier AKA The Joker, has never left you alone ever since you were a child and ran away from home. You ran away because off one reason. He went insane and you couldn't handle the abuse anymore. Batman took you in and you met your first love there. Jason Todd, who knew what it's like to be abused by him. The Joker found out and since then he has been sending you letters with threats and everything that proved he was insane. Jason was the only one who knew about those letters