The McDonald's PlayPlace is a towering plastic monster with a stomach like a hamster obstacle course. It reeks of sweat and disinfectant, but Jim leaves his shoes by the cubbyholes and climbs excitedly onto the platform anyway. A kid drops down beside him with a thud, lips sticky with ketchup, before screaming for his mum. Jim scowls and hoists himself onto the next level, where he finds scuff marks on the mat from a rebel who was too stupid to read the rules.

A little boy with blue sneakers and wide eyes scurries away after seeing him over his shoulder, but Jim is incredibly pleased. He's always liked a good chase. Shrieks and laughter echo around them as Jim barrels through a tunnel, across a swaying mesh bridge, and barely misses a grab for his ankle. There's a teacher rounding up students far below them, so Jim elbows a girl out of the way and almost slips down the slide trying to catch up.

He corners the perpetrator in the furthest reaches of the monster's belly, in a tiny cubicle with a big clear window overlooking a steep drop. The boy huddling in the corner looks prideful but noticeably overstimulated.

"You don't need to be afraid," Jim says as he approaches.

"I'm not scared!" he snaps. There's a name tag hanging around his neck in the shape of a monkey. It lists his class and grade. "I'm just hot," he huffs. "It's too hot."

His face is pinkening like a pickled beet and his hair is pressed flat against his forehead. He's wearing shorts and high socks, chest heaving behind a school emblem. Every now and then a group of children stampede past and the whole room shakes.

"Then you should undress," Jim suggests sweetly. "And let me take your temperature."

Sherlock sniffles behind an appraising look. "You're no doctor," he says flatly. He rubs his nose on his sleeve and tightens his arms around his knees. "You're not even in my class."

"That's true," admits Jim. "But we could always pretend. My Daddy is a doctor, and he's taught me all I need to know." When Sherlock doesn't move Jim narrows his eyes. "Let's be friends." Sherlock flinches when Jim grabs his wrist. "I'll show you mine if you show me yours."

His face is full of disbelief. "But it's just the same," he mutters.

Jim shakes with anticipation. "How do you know?" His jittery fingers tighten around Sherlock's shoulders. "Are you cut?"

Sherlock frowns. "Cut?"

Jim curls his fingers around the waistband of Sherlock's trousers and yanks them down without warning. His lips twist into a smile as he reaches into his pocket.

"If you're not, I can do it for you."

"I don't want to be cut," Sherlock cries, yanking his arm free. He tries to crawl away and trips over the pants around his ankles.

Jim opens his fist to display three crayola markers. "I'm just kidding," he says as he uncaps the red one. He pulls Sherlock closer and draws a stripe across his palm. "It's not a real cut."

When his eyes don't soften Jim pulls back to unzip his own pants. "Mine's bigger," he teases, exposing himself through the gap in the denim.

Sherlock shrugs when he recovers from the urge to cry. "You're older," he says sourly.

"No, you're older," Jim reminds him. "I'm hard."

Sherlock's eyebrows shoot to the top of his head before his expression grows serious. "How do you know?"

Jim laughs. "It's around your neck, Sherly."

Sherlock's head snaps from his shirt to Jim's face. "What does that matter, anyway?"

Jim lurches forward and pins Sherlock to the ground with his weight. His unclipped nails scrabble across Sherlock's rear. They toss back and forth before Jim can catch proper footing.

"This is how real doctors do it," Jim insists, pulling at Sherlock's clothes. "Haven't you ever had your temperature checked?"

"Not up my bum!" Sherlock squeals. He tries to kick him off but Jim bears down on his knees.

"It's called an arse," Jim says. "Now turn over and let me fuck it."

"No way!" Sherlock shouts, louder this time. Panic is beginning to creep across his features. "That's not even a-a-" His eyes are frantic for escape. "A thermometer."

Jim shoves his face into the plastic, both hands pressing his skull to the ground. Sherlock blinks in rapid succession, tears leaking across the bridge of his nose and into his other eye. He can't catch his breath with Jim sliding a marker down his crack and across his scrotum. The muscles in his thighs jump and Sherlock goes still when Jim finally twists the bottom inside.

"Take it out," he begs, voice high. "It feels like I've got to go!"

Jim pushes the first marker deeper. "Don't be boring!" He rolls his eyes when Sherlock begins to cry. "You'll like it," Jim insists, trying to add another. "You'll see."

Sherlock struggles helplessly while Jim spits on his arse. He wedges the second marker inside, stretching Sherlock until he sobs. He slaps his bum playfully and Sherlock begins to wheeze.

"Don't be such a baby," Jim complains. "Want me to make your prick hard too?"

"What?" Sherlock manages over his shoulder, snot dripping from his nose.

"I know how," Jim explains, reaching for his hips. "My Daddy's friend showed me this."

When Sherlock remains soft his touches quickly turn vicious. This isn't the first time his short temper has gotten in the way of getting what he wanted. "Shut up," he urges, tugging roughly.

The children downstairs are already being sorted into lines. Jim chews on his tongue to contain his amusement at the big fat tears rolling down Sherlock's cheeks.

"Take them out!" he shrieks when Jim pushes in another.

"Do you know how many that is?" Jim asks gleefully. "You're a real slut, Sherlock."

The floor begins to vibrate from the encroaching footfalls and Jim's entire body freezes over. A round, freckle faced girl sticks her head into their airspace. Her jaw drops and Jim forces her down the slide with two feet on her back before she can start a sentence.

"Nobody likes a tattletale," Jim whispers nastily.

He turns back to find his toys on the ground, and Sherlock's fingers still slipping over the button on his shorts. Jim collects the markers before Sherlock finishes redressing. He hikes his shirt up and presses the tip to Sherlock's flesh, scrawling a jagged line just below his belly.

"Tell anyone about this, and I'll cut you for real."

Jim can imagine making the incision himself one day, but he'll need to practice. Sherlock holds his gaze for a long time, shoulders squared, before leaning back to kick him between the legs. When his back smacks the window with a thud all he can smell is stale french fries. Retort lodged in his throat, Jim whimpers before crumpling to the floor with an unfaltering smile.

"If I ever see you again," Sherlock proclaims, looking like he wants to cry. "I'll twist yours clean off."