Arkham Asylum.

Terry McGinnis was a member of a street gang and had his fair share of run-ins with cops in his early teens. Years after Batman was last seen, he found himself on the run from the Jokerz, who model themselves after the deceased Clown Prince. McGinnis fled onto the grounds of Wayne Manor, where an aged Bruce came to his defense. The strain of the fight placed substantial stress on Wayne’s heart and he collapsed. McGinnis helped him into the mansion and got him his medication; before leaving, he noticed a bat stuck in a grandfather clock. As he tried to free it, he stumbled upon the entrance to the Batcave. After Wayne kicked him out, Terry returned home to find his father murdered. He seeked Wayne’s help but Wayne, still shaken from years earlier of relying on a gun for self-defense, maintained that he’d given up the cowl, so McGinnis took matters into his own hands and stealed the Batsuit. Convinced there was still a need for Batman, Wayne hired McGinnis as his “personal assistant” and began training him for his new role. It was revealed that McGinnis is Wayne’s biological son due to Amanda Waller’s Batman Beyond project.

Batman Beyond, by Yvan Quinet.