Batman Beyond is the intellectual property of Warner Bros. Animation and DC Comics, created by Bruce W. Timm and Paul Dini.
The Thing in the Basement.
When Bruce found the access to the secret door compromised, he knew it had to have been Terry.
Well, it had to happen someday. The old man drew a deep breath and began the long way down the elevator, Ace by his side, and shaking his head to himself all the way. He was thinking of how he should apologize, or if he should at all. Being Bruce Wayne, even after all these years, his first impulse was not apologizing. Yet he couldn't blame the boy for the reaction he was sure to have. Even so, by the time he had reached the bottom he still hadn't figured what to say.
Still pondering that, he walked over towards the end of the single chamber, hundreds of meters under the foundations of the cave. Terry sat by Bruce's chair, facing the cell and its glass walls, his back turned to the old man. And facing the other old man, who sat on the cell's floor, moving his flaccid lips up and down as if chewing his words with mashed gums. Occasionally he would giggle in absent minded fashion, sticking his white fingers to the glass wall separating him from the tall, vital man.
"T-Terry, yes, that's right, I forgot..." the clown's voice wheezed, a shadow of a chuckle chortling up his throat in vain before collapsing just as soon. "S-Sorry, how many times have you told me already...?"
"Four," Mc Ginnis dry and harshly said, then barked at the other elder approaching from him with the large dog. "I can't believe you. Even now, even after everything, you find ways to surprise me."
"Y-Yeah, that's what he does... that..." the Joker smiled like a spacey child, lifting his unfocused eyes to look at Bruce Wayne. "We have another baby boy! And you never told me, and you never told him of me..."
"And you never told Tim Drake either, I'm sure." Terry was still refusing to look back, at him. "Did you?"
"He's a detective. He knows," was all Wayne said, leaning ahead slightly on his cane. "So does Barbara. Dick definitely knows too, he threw this on my face last time we talked..."
"Which... Which one was Dick, again...?" the Joker babbled, head lolling aside until he almost toppled over as a whole.
Terry turned back at last, eyes burning in anger. "Why weren't you honest about this, all the while that was happening to Tim?!" he demanded of his mentor. "Didn't you think I'd have the right to know we had him right under our feet the whole time?!"
"Who... Who is Tim?" the Joker blinked. "Ah, sorry, you're Tim, aren't you? No, no, you just talked of him in the third person, nnghhh..." he took a feeble fist to his head and knocked. "Thinking used to be so easy..."
"It wouldn't have helped," Wayne looked aside. "There was no way he could have had anything to do with it, all the way from down here. In truth, he's as dead as if he'd actually perished that night. He's been buried here ever since."
A wide, perverse grin worked up the bald man's angular face, slow but steadily, and the clueless eyes fleetingly sparkled with malicious life again. "Ooooo, that night. That, I remember..."
"Why did you save him?" Terry asked Wayne.
"We save lives. It's what we do."
"He didn't deserve to be saved!"
"I did something arguably worse than just letting him die," Wayne growled, casting hateful eyes on the cadaveric wreck of a man sitting on the floor, skin and bones on the baggy suit with no shoes. "I kept him here, coming every week to see him wither and falter. As soon as he'd recovered enough from the shot, he'd spend days howling and menacing me, struggling to get out, and I'd just sit here, blocking his way, staring at him..."
"S-Sometimes he'd hit me for hours too," the Joker reminisced, smacking those toothless gums together. "B-But he loves me not anymore..."
Terry's hateful glare turned back towards him.
"What?" the Joker asked, then coughed. "I was still strong, young, and a looker back then. I'd survived being blown up, falling into vats of acids, being thrown down chimneys, swimming with sharks... a simple spearshot through the chest wasn't going to kill me, was it?"
Terry punched the glass, and the sharp nosed old man backed away, pulling himself back and dragging his carcass along the floor, scared by the noise more than anything else.
"He can't even stand up on his own anymore," Bruce Wayne grimly said. "He'll never hurt anyone again. I'm... not satisfied with that, but it's as much of a closure as I felt I could provide. For any of us."
"Stand up..." the Joker wheezed nasally, gasping for breath after the scare. "I used to love those words... Tom, what year is it now? Bruce never wants to tell me..."
"Shut up," Terry told him.
"A-Ah, s-so you w-were the one to inherit the temper. D-Do you put on the costume now? Y-You look like you work out... Sorry, I think I forgot your name again, it was...?"
Terry didn't speak to Bruce for weeks after that. Eventually, he more or less came to grips with it, and a couple years later, it was him who went down the elevator with the bowl of food.
Somehow, the simpering, doddering mess knew. "Oh. Did he-"
"Your food," Mc Ginnis growled, shoving it through the slit.
The Joker shakily took his first handful of the meal, taking it to his mouth. "I-I-I never thought I'd ever o-outlive him. A pity."
"I mean, a pity that I can't l-laugh anymore. I-It'd be to laugh, but I've forgotten how to. Which reminds me," he looked at him curiously, the mashed food trickling down a side of his mouth, "y-your name, what was it, again...?"
"Just shut up and finish soon, I've got better things to do."
The Joker kept on eating in silence.
"Y-You know," he said after several long moments of swallowing laboriously, "y-you're a much better c-cook than he ever was..."