When Jack was twenty-one years old, Bert left London.

That last afternoon, the leerie had climbed up to the rooftop of the old building they all shared as a home. He had been looking for the Sweep, come to offer him the last of his lunch. Jack was about to go out and do his rounds cleaning out the city's lamps with Angus, but he liked to check on Bert whenever he had the time.

It wasn't that Bert was getting old. Well, he was. His hair was going snow white, slow as you please, and Bert seemed to like it doing that. He didn't try any new-fangled dye and he moved as though he were still in his twenties himself. But he was getting quieter as time went on, more reflective than he'd ever been, and the quieter he got, the more worried Jack became. You could call his old friend a lot of things, but introspective was hardly one of them. Bert liked to let the world know he was there, that he cared. If he wasn't making some sort of sound, be it a belly-laugh or a whistle, there was bound to be something wrong. Jack found himself making sure Bert smiled more often, making sure he had someone to talk to should he feel like talking. But he rarely did. He would always good-naturedly wave away the offer, as if nothing were wrong.

The truth was, Bert had been looking sort of out of place for a while now. Not lost, exactly, but tired of standing still. For someone always moving, always living, Bert seemed to recognize some stagnation in his world. You would never know he had been waiting, all this time, if he had not slowly been coming to the decision not to wait anymore. To move along. The Handymen, the Sweeps, all of them, had been feeling it from him recently. They hadn't been able to identify it yet.

Jack reached the rooftop, saw the sack in Bert's hand, and knew. But he didn't want it to be real, so when the older man turned to greet him, he held up the half-finished tin of soup he'd carried with him and raised his eyebrows.

"Left you a bit," Jack explained. "Might be a bit cold now…" He couldn't find any more words, eyes fixed on that sack. It looked slightly heavy.

Bert was no longer wearing his gray cap, and the wrinkles by his eyes had multiplied, but he still appeared young when he smiled. "Many thanks, Jackie," he replied, just as casually. "Mustn't go on an empty stomach, eh?"

Jack's shoulders sagged very, very slowly. He set the tin down, feeling all his breath leave him without a sound. "Where y'headed?" He tried to sound chipper, like Bert was just going for a midnight run along London's roofs with his mates.

"Here an' about," was Bert's vague response. "Travellin' at last, seein' what's out there to see."

The lamplighter stared at him, trying to hold down every detail of the person he loved best in the world. He was grown now—properly grown. There was a hint of stubble on his chin and around his mouth, and only the jacket Mary Poppins had given him so long ago had seemed to grow with him. Gertie was, at last, just his size.

But being around Bert made Jack feel eight-and-three-quarters again. They were the same height (or thereabouts) now. Jack could handle the ladders easier than Bert could. Yet it changed nothing, not really. Not at the heart of things. He still looked at the Match-Man as though he knew everything there was to know in the world, and the Match-Man still looked at Jack like he was his prized possession. His best broom, his most lively dancing shoes, his favorite pastime.

Pride was, even now, leaping in those twinkly old eyes. Bert never looked tired. "I won't be needin' much." He held up the sack and shook it. "But they say it's best to take a bit o' home with you, wherever y'go."

Jack glanced at the clouds, thinking how bothersome it was that grown men were not supposed to cry. He pressed his lips tight together before asking evenly, "Think you'll find 'er?" Shifted his weight from foot to foot. "Out there?"

They didn't say Mary Poppins' name. They hadn't, for a long time. Bert had taken to talking about her at night, at least twice a month, sitting on this very roof with only Jack to listen. Even then he never said it. But each always knew who the other meant.

Bert's eyes dropped to the ground and back up again in an instant, and he took in a quick breath. "Oh, I might do." He strolled closer, nodding too. "Might do. But I won't be lookin' hard, will I? No, if she wants me," he added, letting that breath out, "she'll know where to find me, somehow or other. Wherever I end up."

So Mary Poppins wasn't the reason he was leaving. Or maybe she was—maybe London was too heavy with her fingerprint for Bert to stay any longer. Either way, Jack knew not a word would stop his old teacher from getting on whatever train he wanted and moving so fast, so far away.

But that cheeky, eight-and-three-quarters street urchin insisted he try anyway. Jack took a few unsteady steps of his own forward. "You could stay," he said, wishing he had more enticing words, something to really carry. "I could—that is, we might try somethin' new. Somethin' else."

"Somethin' else!" Bert repeated, eyebrows drawing tight and low. "We been lots o' things, my lad, but I think we know what you're settled as. The best leerie in town, try somethin' without a bit o' light an' polish? Bite your tongue!"

Jack took Bert's sack right from his hand, carrying it the way the Sweep used to carry the ladder, back when it was still bigger than Jack was. "Then I'm comin' too. When are we off?"

He lifted his head up in a slight challenge, a joyful, hesitant smirk starting up.

Bert looked Jack in the eyes for a long time then. There was so much love and so much life in those eyes, Jack wondered how he had ever thought anyone else's could be really magical. There was no gaze, no face, he better acquainted with magic. Long-gone angels on balconies and longer-gone flying nannies and all. His smirk faded, little by little, losing ground with the aching in his chest. He knew what was coming.

A calloused hand reached out and held his arm. "Sorry, Jack. I'm afraid this's as far as you go."

So Jack let the sack hang in his hand, then make the barely-there drop to the floor. It was getting more real with every second. He did try to keep it all in still, blinking furiously at the stinging in his eyes.

Bert opened his arms and Jack moved forward easily, wrapped in a tight hug that smelled like soot and nighttime. The leerie squeezed his friend hard, squeezed his eyes shut harder, thinking he might wake up and be thirteen again on Kite Day in the spring. Then Bert wouldn't be leaving. They'd have years left.

"No blubbin', now," Bert said into his shoulder, mock-stern. "I don't wanna see one shred o' sorrow outta you, got that? No self-respectable leerie walks about sad! It's bad for business."

Jack could feel himself nodding, but wasn't sure he could obey this time. "Y'don't have to go," he said, eyes still closed. Breathing in the smell of Bert's jacket. The smell that would hit him every night before he fell asleep as a child, letting him know he was cared for.

"Aw, don't take on so." Bert held him at arm's length, looking the younger man up and down. He clicked his tongue—the click seemed to see just as much potential as it had seen when they'd first met. "Here, you'll be all right. Be a regular Pied Piper, you will!"

Jack brushed angrily at his eye with a thumb, staring at Bert's shoes. He kept nodding. Why was he nodding? For once, it wasn't as if he agreed.

"But not wi' that head down." Bert shook Jack by the shoulders, just a little. "Look up, Jackie. That's the thing to do. Always look up. Never know what's waitin' round the bend." He reached down and took up his sack. "I know I don't!"

The wind picked up and Jack tried to smile, but it seemed the breeze whipped the effort away from him. Bert's white fringe brushed over his eyes for a moment, and the Sweep smiled broadly. Beneath them, London was a bustle of activity, unaware that it was soon to lose its best Tradesman. The Milk Man was below, on his way to Cherry Tree Lane. It wouldn't be long before the Admiral fired his cannon, a touch late, as he had been for years now. And the baker would be pulling fresh bread from the oven; they could smell it even from where they stood, attuned to every piece of the city. They were threads in its pockets. Bert especially. How could he go?

Suddenly, after some deliberation and chewing the inside of his cheek, Bert opened the sack. He reached in and pulled out his cap, the same cap he'd had on when they'd met. It was gray, and he handed it to Jack.

"Always good to 'ave a spare. Case y'meet some little bloke who needs it someday."

The leerie's mouth opened just slightly, holding the hat like it was made of gold.

"It's your city now, son. Take care o' our pals," Bert ordered him, clapping him on the shoulder lightly. Rubbing up and down like Jack was still small enough to catch cold on a roof. "And watch out for the Admiral, 'e's a bit off-target lately."

Jack sniffed, straightening. "Right."

"And if y'see Mary Poppins…"

There was a pause, both of them still and quiet and letting the wind hit them. Jack waited for orders, not entirely sure what he might hear next. But Bert was grinning, no trace of bitterness. He would probably never have it in him to be cross with her, even over having to wait this long.

"Tell 'er she looks lovely."

Jack grinned back, making an effort to put his heart into it as usual. "I will."

Bert slung the sack over his shoulder and headed for the ladder leading back into the building. Before he stepped down, he glanced up, squinting at the sky.

"Miss ya," Jack made sure to call, lifting a hand. Suddenly he didn't feel so low. The Match-Man seemed more alive at that moment than he had in years.

Bert's attention bounced back to Jack with a crooked smile, then up again. "Wind's in the east," was the last thing he said, thoughtful and slow.

He made his descent, and the wind appeared to fade with every rung his feet hit, every inch of him that disappeared. Jack could have followed him down. He could have gone all the way to the train with his old mentor, but something kept his feet glued to that spot. It would have felt like cheating, dragging at every last second with the Sweep, right up until the vehicle was out of sight.

Jack whipped off his old cap and pocketed it. Then he dusted off Bert's—Jack's, now—and tugged it carefully over his hair. He strolled to the edge of the roof. And instead of looking down to try and catch a glimpse of the chimney sweep on his way to the station, Jack followed that last bit of advice and looked up. The clouds were parting and the sun was beginning to peek out into his eyes. He pulled the cap further down.

It was a perfect fit.