Cannonball opened the door to the world Above in his usual style, causing it to hang listlessly from its one remaining hinge as dust settled in the air. Mender and Coats ducked under his huge arms as they too emerged from the door, and stared upwards into the night sky. It was raining lightly, and a fine damp mist curled around the alley where the three of them stood and breathed deeply in the fresh air.
"Every time," Coats mumbled to herself. "Every time, it feels so good up here, and I feel like I don't want to go back..."
Mender shot her a sharp look across the belly of the giant lad who stood between them. Inside her own head, Coats cursed. She hadn't been as quiet as she thought she'd been.
"So, we're going, right?" rumbled Cannonball's voice at last, as if he'd spent the entirety of the time between opening the door and now just thinking up that one question.
"Yes," Mender replied, voice like acid. Coats just nodded. Best not to think about the elusive promise of the world Above - after all, all three of them had rejected that promise when they were young. They'd chosen of their own accord to live Below. Hadn't they?
By the time they had reached their target, their canvas for the night, any antipathy that the three felt towards each other had melted away. In the cut-and-thrust world of the Underside a divided tribe was a destroyed tribe, and their old habits were too ingrained in their minds to be given up on after just a few moments Above. Each of them reached for a brush or a spray can as they stood beneath the towering marble of the wall, and each of them became in an instant an artist; three kindered spirits joined by loyalty, passion and ability.
The Art began.
The wall stood gleaming and glittering as they finished their task. Purples, blues and greens all merged and parted amidst the silver and gold sparkling reflections, giving life and depth to a surface formerly flat and clinical and dull. They each looked at each other, and smiled. A good night's work, as always.
They turned to leave, but stopped suddenly. Beneath a straggly brown fringe and above a mud-splattered t-shirt, two emerald green eyes glared at them as if they were piercing them to the depths of their soul.
"Wh... who're you?" Mender stammered, caught off-guard by his own failure to notice the child earlier.
The child, if that was indeed what it was, mumbled something that none of them heard.
Coats knelt down next to him in the road, bringing her own head level with the kid's. "It's okay," she said in her best attempt at soothing. "You can see us, right? What's your name?"
The child whispered in her ear, much to Mender's annoyance.
"Are you lost?" Coats asked.
He nodded, twice.
"Do you know where your parents are?"
"Are you cold?"
Coats sighed, and stood up to face her friends. "He'll die out here in the cold and rain before long. We're not leaving him."
Cannonball's face slowly twisted into a mask of confusion, while Mender responded with practiced quickness.
"Dun' be stu'id, Coats."
"I'm not being stupid, Mender, I'm being human!"
"Shut up. Look, I'm the eldest, what I say goes. I'll take responsibility for him."
"Huh. 'e's prolly got parents lookin' for 'im even nah. Look' like a weak kid. 'ow's 'e gonna survive B'low?"
"We'll look after him."
Cannonball looked like he suddenly understood, and he echoed Coats' words. "We'll look after him."
Mender looked at the other boy, then looked up and made eye contact with him. Cannonball was at least a foot taller, and verging on being spherical. "Of course he'd side with Coats," Mender lamented as he sighed and turned away.
So it was that the young boy, abandoned on the streets of London Above, came to find a new home Below. Already fourteen years old - the eldest of her tribe, but soon to be too old to remain with them - Coats spent her last year or so teaching her young apprentice everything he needed to know to be a member of the tribe and to survive in the gloomy world beneath the streets of the capital.
Her last wish before leaving was that the boy be initiated as a full member of the group, at a ceremony called the Naming. Just seven years old, he stood before the entirety of his newfound society. Already an athletic kid keen on play-fighting, Coats chose for him the name "Knife".
Shortly after the ceremony, Coats disappeared for good. Most say that she disappeared, along with her vast array of cold weather wear, into the frozen January world Above. Others, of course, keep the rumour alive that she still to this day roams the caverns of the subterranean world, as a Guide, a courier, a secret agent, or hundreds of other possible occupations.
Time blurs a little in the world Below, but that was thought to have been somewhere between six and eight years ago. After Coats left the tribe, Mender became the eldest and thus leader. After him, a succession of kids ascended to the title one after another, until the responsibility at last fell to Knife. Now fourteen years of age, just as Coats was when she became his mentor, Knife has not long left as a member of the tribe. But that doesn't matter to him, just like it's never mattered to a tribe leader before. All that matters is the fun, the adventure, the tribe, and the Art.