Bruce eventually gets used to having Jack at the reconstructed Wayne Manor.
That isn't to say that the two don't have their difficulties – Bruce never really forgives Jack for Rachel, and Jack thinks of Bruce as an almighty idiot – but they manage to be civil on those rare occasions they're stuck together.
The Memory Potion that Jack's still taking help with that. He was rather fond of Bruce, before he forgot about him, so he doesn't find it that difficult to be civil. He still can't resist riling him up every so often, but he doesn't do it often enough to get himself thrown back in Arkham.
After about six months of weekend visits, Bruce finally agrees to have Jack at the Manor full-time. The authorities allow it, provided that Jack doesn't leave the grounds and that there's always someone on the grounds with him. Jack's not fond of the 'babysitter stipulation', as he calls it, but anything's better than Arkham, so he agrees.
Eventually, the Memory Potions lose their effectiveness, and Jack and Hermione agree that this is probably because they've done all they can. His mind is still a little broken, the darkness of the Joker lurking in the basement of his mindscape's haunted house, but he's better behaved than he was.
His meditation further improves the control he has over the madman. Two months after Jack is released into the care of the Waynes, he finally understands the Joker, and in that moment he remembers what happened to make him the way he was.
Jack was in London at the time. He wasn't sure how he'd gotten there, but there he was, facing off against a pair of wizards in black cloaks, their faces obscured by skull-shaped masks.
"Look at this," one of them sneered. "An Ilvermorny dropout. How sad. Bet he doesn't even have a wand to protect himself."
"Prob'ly not," the other one agreed. "Easy target. Maybe too easy."
They looked at each other and shrugged, then advanced on Jack. "Good enough for me. Crucio!"
The worst pain Jack had ever felt in his life – pain akin to the day the day he'd received his scars, but so much worse – blossomed all over his body. Jack bit down hard on his cheeks to keep from screaming, and the taste of blood coated his tongue.
Finally, timeless time later, the pain stopped, leaving Jack on his hands and knees in the alleyway. The pair stood over him and laughed, one lashing out in a kick that knocked Jack over onto his side.
What followed was an endless stream of pain. Eventually, Jack stopped screaming and started laughing. The pair who were torturing him paused, allowing Jack to stand.
He was still laughing as he carved permanent grins into their faces, leaving them for dead in the alley.
"Come on, Jack!"
Hermione pulls him through the crowd, eager to explore. Jack stumbles along behind, rolling his eyes good-naturedly at his girlfriend's antics.
"Slow down, beautiful. The stores'll still be there if we get there in five minutes or an hour."
She turns back to him, narrowing her eyes. "Don't give me that tone, Jack Napier! I know you're as excited as I am to see the bookstore."
He grins sheepishly, running a hand through his still-greenish curls. "You got me."
The pair have – after almost a year of legal deliberating – made a trip to Hermione's native England, to see the magical communities there. Their first stop, since they are in London, is to visit Diagon Alley, which Hermione had read was hidden behind the Leaky Cauldron pub.
Finally spotting the pub, Hermione makes a beeline for it, once again dragging Jack in her wake.
They pass straight through the bar. In her excitement, it takes Hermione three tries to tap the right brick with her wand. It doesn't help that Jack is distracting her, kissing down her neck as he watches her wand tip shake.
"Jack! Stop it!" she hisses as she finally taps the right brick and opens the way to Diagon Alley. He laughs at her, straightening to his full height and taking her hand again.
"Come on," he teased, "the stores won't be open forever."
They stop by Gringotts first, in order to change some of their American money for Galleons and Sickles and Knuts. Hermione had gone on a long rant about how ridiculous a form of currency the old coins were – in America, they had a dollar equivalent that was split into hundredths, like most sane currencies – but now there was no sign of that anger. In fact, the only hiccup in their visit to the bank is when Hermione argues over the currency exchange rate, stating that the number of Galleons ought to be greater according to her research into it. The teller confers with another goblin for a moment, then grudgingly agrees to giving her a better price. They leave to some impressed looks from bystanders.
As they get out the doors to the bank, Jack stiffens. Hermione turns to look at him to see him intensely focused on someone in the crowd. She's not sure why, until he turns his head and she gets a better look at him.
The man has a scar like Jack's. She'd bet some of her newly-gained Galleons that the man has an identical scar on the other side of his face.
The man turns his head even further and catches sight of them. He does a double-take, staring straight at Jack. He raises his wand.
Hermione is too quick, though. She raises her own and Stuns the man. She and Jack dash over to see who the man is, as his companion casts an Ennervate to wake him up.
The man sits up, and suddenly Jack is standing over him again, knife in hand. Hermione's not sure where he got that – she certainly didn't give it to him – but at least it's not in the other man's mouth.
"What are you doing?" the man's companion, another man with long platinum-blond hair, splutters. "Do you know who we are?"
"I don't know about you," Jack retorts, "but this, ah, this man... he's an old... friend."
"Yaxley, is this true?"
Yaxley stands and glares at Jack. "I've seen this filth before. He was the one who gave me these." He indicated the scars on his face.
Jack frowns thoughtfully. "Hmm... Nah, don't remember that. You just look like a vaguely familiar piece of trash."
Yaxley turns beet-red and raises his wand again. "Call me trash again, freak."
Hermione raises her own wand again. "Don't threaten us."
Jack raises his hand to stop her. "Don't worry about it, beautiful." His eyes narrow at Yaxley, and he pushes his sleeves up. "I got it all handled."
Yaxley's mouth opens, but before he can speak to cast, Jack's knife is in his mouth.
The silence is such that one could hear a pin drop. Yaxley's friend pulls a wand from his cane, but finds Hermione's wand pointed at his face, so he stays out of it.
"You wanna know how I got these scars?"
When Yaxley doesn't answer, the Joker frowns. "Well. I was just a teenager. Mommy always told me not to go out after dark, but I didn't list-en. And wouldn't you know it, that was the day the loonies were let out of the bin."
He shifts slightly, his grip sliding from Yaxley's collar to his neck. "One of the crazies grabbed me. He told me that it was such a beautiful day outside, everyone should be looking happy! I tried to tell him it was night, but, well, you know how well those kinds of people take to being told they're wrong.
"Out of nowhere, he had a knife. He asked me why I wasn't smiling. How could I not be perfectly happy on such a beautiful day? He offered to help me smile more, and, innocent little teen-age-er that I was, I agreed.
"So he took his knife, and, well..."
Suddenly, Yaxley was on the ground, his scars reopened and howling like a man possessed. His friend was about to cast, but Hermione dropped him with a Stunner to the face.
The Joker looked around at the bystanders. "Well? What are you look-ing at?"He made a 'shoo' gesture, and the crowds dispersed.
Hermione rounded on the Joker. "What was that for?"
He kicked Yaxley in the stomach. "This trash," Jack snarled, punctuating his words with more kicks, "is the reason I went so crazy. If not for him, I'd still – be – Jack!"
Hermione darted in close to him, avoiding his knife, which was swinging wildly with his movements, and placed her hands on his shoulders. "You still are Jack," she said in an undertone. "You are. You remember now, who you are. You have to calm down, Jack. Some of those bystanders are bound to call the authorities, and you can't still be the Joker when they get here. Remember your meditations."
"Right." He closed his eyes and his shoulders relaxed, Hermione's hands sliding off him.
By the time the red-robed Aurors arrived, Jack was calm, and he and Hermione were standing beside an unconscious Yaxley, Hermione having Stunned him so she could stem the flow of blood without his flailing getting in the way.
The Aurors took Jack and Hermione back to their headquarters in the Ministry of Magic to question them about the events. They ended up letting the two off with a warning after eyewitness testimony stated that Yaxley had raised his wand first. They did, however, confiscate Jack's knives – all of them. Or at least what they thought was all of them.
Hermione regretted casting those Undetectable Extension charms on his coat.
They returned to the Leaky Cauldron, where they made arrangements to stay for the night. They then wandered the shops for an hour or so before they closed for the night.
After a hearty meal, they retired to their room. Hermione and Jack lay together in their bed, staring at the ceiling, each caught up in their own thoughts.
Hermione was so caught up that it took her several minutes to even register the ring Jack was holding in front of her face.
He grinned. "So, will you?"
"Will I...?" It took her a second, but she finally caught on with a blush. "Of course I will."
"Good." He slid the ring onto her finger. It was a perfect fit.
They fell asleep together, smiling like fools.