While hallucinating, Batman makes a passing reference to Jason Todd, the second Robin. Batman raves "Robin... look out... Joker's got a bomb!", which in the comics is how Jason died. See more
"There's always time to heal", the doctor told me, but he was wrong. There was no time left. Not for me, not for him, and not for Gotham City. And as long as I remained trapped in Arkham, there was nothing I could do, except wait for the end and remember the beginning.