Batman remembered it as if it were yesterday, staring down at the corpse of his nemesis, and wondering what to do next. The Joker's beaming smile, frozen forever on his lifeless face, seemed to mock him somehow – even in death, he had the last laugh. He knew nothing would ever be the same again, not for Gotham City, and not for Batman.
And he had been right. Batman had never credited Joker with any great wisdom about anything, but Joker's death had changed everything for him. Harley Quinn had attempted one last revenge scheme against Batman, but had been foiled by Robin, who came to rescue him from her clutches. Batman knew he would, but he almost hadn't wanted him to.
It would have been justice, to pay for Joker's life with his own. Even though Joker had technically brought about his own death, Batman blamed himself for not being able to save him. His guilt at Joker's death was now added to the guilt he always carried for his parents' death, and guilt wasn't rational. Of course an eight year old boy couldn't have stood up to a mugger any more than Batman could have stopped Joker from stabbing him and making him drop the vial with the cure in it. But Batman had never been entirely rational, and he felt incredibly guilty about what had happened, not just to Joker, but to Talia.
The only reason Talia al Ghul had been at the Monarch Theater had been to save Batman. She loved him, and because of that, she had died. Batman had put her in Joker's crosshairs. That seemed to be consistent with anyone who loved and cared for him – they would die, either by his enemies' hands, or by the neglect of his own. His parents, Jason Todd (his second Robin, murdered by Joker), Talia, and now Joker himself. He felt responsible for all of them, and he didn't know how to live with the guilt anymore.
So he withdrew into himself. Robin, Oracle, Nightwing, and especially Alfred had expressed their concern to him about it – he communicated even less than usual, and that was saying something. Batman knew he was on the edge of a deep depression that threatened to consume him – he knew if he got pulled into that abyss, he would never come out of it. But he couldn't bring himself to fight the darkness anymore. And that was the worst part of the depression for him – the apathy.
He had trained Robin well enough to take care of any of the criminals seeking a vendetta against him – Harley had disappeared after her attempt, but Two-Face, Penguin, Riddler, and many others still sought revenge for their perceived humiliations during Arkham City. But Batman couldn't bring himself to take any interest in it. He spent his days and nights brooding alone in his manor, turning into a complete recluse. Efforts to engage him in reality again proved fruitless. Efforts to remind him that Gotham needed him fell on deaf ears – he just responded that Robin could take care of it, which was true. Batman felt superfluous to his own existence, and he was apathetic even about that.
Time wore on. Robin and Oracle got married – Batman sent a gift to the wedding, but didn't attend in person. Alfred got older and more frail, unable to do all the tasks he was accustomed to, so the manor fell into a state of disrepair, which Batman didn't care about. Nothing anyone could say or do could draw him out of the pit of despair he had sunk himself into. Until one day.
One day, Robin entered the Batcave to find Batman there, flitting in between his chemistry set and the Batcomputer. It was unusual to see Batman down here, and even more unusual to see him working, and Robin was both shocked and pleased.
"Hey, Bruce, great to see you!" said Robin, sincerely. "What's the occasion?"
Batman ignored him, studying the screen in front of him. "Doing some kinda experiment, huh?" pressed Robin. "What's that on the screen?"
"Blood sample," retorted Batman. The two words were more than he had spoken in a long time.
"Whose blood?" asked Robin, eager to keep the conversation going.
"Mine," retorted Batman.
"Oh. How come you're analyzing your blood?" pressed Robin.
"There's something wrong with it," retorted Batman.
"How do you know?" asked Robin. "I mean, if you're just analyzing it now."
Batman looked up at him. "I feel…happy," he muttered.
Robin stared at him, stunned. "Well, that's great news!" he exclaimed. "And it's about time, I gotta say…"
"You don't understand, Tim," interrupted Batman. "I've never felt happy. Not since my parents…" He trailed off.
"Bruce, being happy is no bad thing," said Robin. "It's great that you're feeling anything after feeling nothing but guilt for so long…"
"You don't understand, Tim," repeated Batman. "I'm not happy. None of my circumstances have changed, so why would my feelings change after so many years of feeling nothing? Why would I suddenly feel happy?"
"Well, maybe you've changed your perspective," said Robin. "A lot of life is based on your attitude toward it, and if you have a positive attitude…"
"I don't," interrupted Batman. "That's the point. Nothing external has changed, so something internal must have. There has to be a chemical reason for this imbalance."
"Maybe you've just changed your state of mind," suggested Robin.
"Maybe there is something wrong in my mind," agreed Batman, studying the screen again. "Maybe that's it."
"Bruce, it's not wrong to be happy…" began Robin.
"It is when I'm responsible for the deaths of so many people," interrupted Batman. "What sort of unfeeling psychopath would be happy about that?"
He flinched suddenly, whirling around. "What is it?" asked Robin, concerned.
"I…I thought I heard something," stammered Batman. "A…a strange…laugh."
"Laugh?" repeated Robin. "I didn't hear anything. I think you might be hallucinating, Bruce, which isn't surprising considering how much time you've spent on your own…"
"There it is again!" exclaimed Batman, looking around desperately at nothing. "I know that laugh, I…" He froze, his face falling in horror at the sudden realization. "No," he murmured, staring at the screen. "No, it's not…possible. It's been years…it's been…infecting me for years."
"What's been infecting you for years?" asked Robin. He glanced at the screen, but didn't see anything out of the ordinary.
"He has," whispered Batman. "That was his plan all along."
"He?" repeated Robin.
"Joker," murmured Batman.
"Joker?" repeated Robin. "But he's dead, Bruce. He's been dead for ten years now…"
"And that's why I can't be rid of the infection – it's had ten years to spread and grow and mutate," whispered Batman. "Until it destroys me completely from within."
"Bruce, I don't see any signs of infection here," said Robin, pointing at the screen. "And I don't know of any diseases that are symptomless for ten years, let alone ones whose symptoms include making you feel happy. Are you saying Joker created a disease like that and he infected you with it before he died? Because I didn't know he had those sort of skills…"
"I need to be alone," interrupted Batman, turning abruptly and storming out of the Batcave. But he had realized in his heart that he would never be alone again, not until the day he died.
Five more years passed, and Batman shut himself away even more – security footage showed him working desperately with chemicals in the Batcave until Robin or Alfred appeared, and then racing off. If he was forced to interact with people, his behavior was wild and erratic, with rapid mood swings. It wasn't unusual for Batman to be sullen and irritable, but neither Alfred nor Robin had ever seen him euphorically happy before. Sometimes he would burst into fits of laughter, which was genuinely frightening. Robin tried to press him more about this disease he claimed to have, but Batman refused to talk about it, and nobody could get near enough to get a sample of his blood to test it again. It seemed to both Robin and Alfred that Batman had grown paler and lost weight, but that was to be expected when locked up indoors for years at a time. They could never have guessed the truth – nobody could have, because it was too horrible to believe. He was turning into Joker.
"Thinking about the day I died again, huh?" sighed a familiar voice, breaking Batman out of his thoughts as he sat alone in his bedroom. "Good times."
Batman sighed. He had been hallucinating Joker for the past several months – at least, he thought it was a hallucination, but he knew his own grip on reality was tenuous at best. He knew it was useless to tell him to go away – Joker didn't listen, and he never had. He had tried ignoring him when he first appeared, but that didn't seem to work either. And so now he was left with no choice but to engage with him.
"Talk to me, buddy," said Joker, taking a seat on the bed next to him. "What's bothering you?"
"I'm just trying to figure out what to do," murmured Batman. "How to end it. I can't bear waiting around for the end anymore, and I know I have to do it before you can take over completely. But I don't know how to do it."
"Oh, there are all kinds of fun ways to commit suicide!" chuckled Joker. "Shooting, stabbing, hanging, jumping, drugs, gas, or my personal favorite, electricity. I've always loved a light-show. But I don't think you can do it, even if you really want to. I know how squeamish you are about killing people, and I think that includes yourself. But even if you do find the courage to do it, I won't let you. You know how strong I've become – are you sure you can kill yourself when I'll be trying to prevent it?"
"Why?" asked Batman. "Why won't you just let us die together? That's what you want, isn't it? That's what you've always wanted."
Joker giggled. "Let's just say I've got another ace up my sleeve I want you to appreciate. I know you think I orchestrated this infected blood thing, but the truth is, I just got lucky with that. I had no idea pumping you full of my blood would allow me to live inside you in the form of a disease that slowly takes over your mind and replaces you with me from within – that's a little too nerd sciencey for my taste. But it was a pleasant surprise for both of us, don't deny it. You had no will to live without me, and now look at you! Frantically trying to create cures for me, working away in the Batcave just like old times! I've always been your reason for being, Bruce, and I always will be. That's why I planned out the aforementioned ace up my sleeve, because I knew you wouldn't be able to function without me. It was my insurance if I died – of course I had faith that you'd find a cure and save me, but I guess it's always good to have a backup plan in case faith has a nasty accident, huh? Sad that your heroes always end up disappointing you, but that's life, I guess."
"There's nothing you could have planned," retorted Batman. "You're dead. Your body was burned, so you can't be brought back with a Lazarus Pit, not that Harley knows about those anyway."
"Getting warm," said Joker, nodding. "It does have something to do with Harley."
"She's left Gotham," said Batman. "She disappeared after Robin rescued me from her steel mill death trap."
"Yes, something you saw in the steel mill," said Joker, nodding again. "Think back deep into the reaches of your subconscious, Bats. Think back to the night I died."
Batman did – he remembered confronting Joker, or rather, Clayface impersonating Joker, in the steel mill before Strange bombed it. But that hadn't been Joker, and Batman doubted Joker scripted Clayface's lines for him - a ham such as Karlo would never allow that. So it couldn't have been anything he said or did…maybe something to do with the missile attack…maybe it had revealed something hidden in the steel mill…a secret compartment or…
"Way off base," interrupted Joker. "And speaking of bases, there's another hint. Rounding all the bases and getting to home plate after knocking the ball out of the park, as it were."
"I have no idea what you're talking about," retorted Batman. "Just tell me."
Joker shook his head. "Nope, nope, nope, don't want to. Won't spoil the surprise like that if you can't figure it out for yourself. But maybe I can guide your thoughts in the right direction…"
Batman saw the manager's office in the steel mill again in his mind's eye. He saw the Harley statue next to Harley's costume from the asylum, and at the foot of the costume…a positive pregnancy test.
"No," he murmured. "No, it was…a false positive. I saw that later in the steel mill – lots of pregnancy tests, and all negative…"
"Psych!" shouted Joker in his ear, causing Batman to fall back. "Harley set that up to throw you off the scent! She's a shrink, so she knows how people think, and she was smart enough to use her shrink skills to fool you. She knew you'd seen the positive test she stupidly left lying around, and she knew if you thought she was actually pregnant, that you'd never leave her or the baby alone. You'd try and take it away from her, to protect it, which is hilarious when you think of your track record with children. So she staged that little setup for you to find, making you think it was a false positive, and that she'd just lost her mind from the grief of losing both me and her hope for my child. But the truth is, that intrepid little Joker sperm found its way to an egg, and made a Joker baby."
Batman stared at him in horror. "So…your child is…"
"About fifteen now," finished Joker. "His mother probably thinks he's old enough to know the truth, and to continue the family business of destroying Gotham and killing you and everyone you love. I say he, but it could be a girl – of course I don't know the sex, having never seen the child. I've been stuck here with you since its birth. I'm not picky – it doesn't matter to me what the kid is, because I'm sure it's inherited my particular set of skills. If there's one thing the Joker line is good at, it's killing and maiming your little Bat-family, and I'm sure Harley has taught it well. That's the punchline I want you to see before you die, Batsy, or at least, before I consume you. I want you to see my child carrying on the Joker legacy of destroying your family, with its proud papa watching on, and with you unable to do anything to stop it. It's still a child, after all. How do you fight an innocent child? You can't beat it into submission like you usually do – your conscience would never allow you to abuse a child like that. So what do you do? Because you can't fight it, and being my kid, you can't reason with it. So you're just going to have to sit back and watch it put on a show. And if it's anything like its daddy, it's going to be a doozy."
The Joker's mocking, hysterical laughter surrounded Batman outside and in – he put his hands to his ears to try to drown him out, but it didn't do any good. Because he was the one laughing.