The harsh solidity of concrete is a large part of its charm. Its brutality; its hardy brawn, set it apart from other building stuffs. Concrete doesn't burn. It's non-porous. It's high performing in most circumstances.

Until you subject it to extreme heat.

You see, while cement plus water plus sand equals the strength and reliability of concrete, concrete plus extreme heat equals cement dehydrating. Dehydrating cement means irate water vapour, trapped in a non-porous prison, desperately looking for an escape route.

Tick, tick, tickety, tick, boom.

Isolde Delacourt hears the explosion a split second before she experiences its impact. It is loud and aggrieved, rumbling through ears and chest cavity like thunder on the war path. For those unfortunate souls standing anywhere near the black-and-white-tiled unisex bathrooms on the lower ground floor, its effects are immediate and catastrophic.

As the over-pressurisation wave meets bodies, lungs are blasted; middle ears and eyes rupture; abdomens haemorrhage. Concussion occurs without any physical sign of head injury. Secondary afflictions, many of them fatal, arrive in the form of flying debris and bomb fragments. Bodies are flung like boneless frisbees across an open field. Except the field isn't open. It's full of concrete columns, and furniture with sharp edges, and people.

So many people.

Issy doesn't see any of this, but she hears the screams and the moans and the muffled panic which follow the roaring explosion on the floor above. And she feels it. First as a sound wave, then as a sharp, jagged pain near her hairline, and wet, sticky blood running down her face – the result of spalling on the underside of the slab above Isolde's head.

Where's my sister?

Saph?

Please be okay.

Something solid and warm holds Issy, and she pushes against it, wishing the room would stop spinning.

"Hey, hey, I've got you, babe. Hold still, you're really bleeding."

She recognises his warm honey voice, but her vision is blurred by nausea, blood, and flickering lights threatening to die at any moment. The boy keeping her upright swims in and out of focus as Issy struggles to remember who he is.

We were kissing... He's golden sunshine pretty and he made me laugh... Griffin. He's Griffin. He's here with his friend Beck.

Saph's with Beck.

Need. To. Find. Saph.

Ignoring her pain and general fuzziness, Issy cranes her neck to look beyond Griffin, frantically searching the crowd for her baby sister's wild, curly blonde hair.

Leather pants, black and white bralette, that vintage velvet jacket she loves so much. Where is she?

Unsurprisingly, Issy hears Seraphine before she actually sees her.

"Get your effing hands off my sister, a-hole."

Approaching at a run and fuelled by adrenaline, Saph shoves Griffin's shoulder much harder than their comparative size should allow. Caught off guard, Griffin stumbles away from Issy but recovers quickly. He offers Saph raised palms and a conciliatory expression that says 'Don't shoot'.

Issy is older by a full three years, yet Seraphine treats Isolde like she's made of dragonfly wings: elegant, delicate and absolutely useless in a storm. Isolde oscillates between resenting this deeply and actively encouraging it.

Because sometimes play-acting is easier than telling the truth.

Sometimes the protector is really the protected, even if they don't know it.

Tonight, Issy's just grateful to have Saph alive and well and by her side. Even if she is spitting like an angry cat.

"Iss, you're bleeding." Fury and fear wage a battle in Saph's voice. "We have to get out if here, Iss. If that explosion was deliberate, it may have been intended for you. Can you walk? You're swaying. Don't you dare pass out on me. Crap. I have to stop this bleeding. Why is there so much blood?"

"I'm okay, Saphs you don't–"

"Use this." Beck yells to be heard over the evacuation siren now screaming its distress throughout the building. Stripping down to a tight, white singlet and black ink, he offers his shirt to Saph, who promptly applies it to Issy's head with a pressure that burns like a brand.

"Arghh... Pluck-a-duck. That hurts Saph."

"Don't be such a princess, Princess." Saph's expression is half glare, half apologetic smile. "We really do need to move, Iss. You up to it?"

Isolde nods and makes to step forward, instantly regretting it as the room does a figure eight without her permission.

"I'll carry her," Griffin offers.

"You'll do no such fu–"

"Let him help, Seraphine. We need to get out of here and your sister can barely stand." Beck places a hand on Saph's arm, and to Isolde's surprise, Saph doesn't immediately shrug it off.

"You hurt her, I'll kill you," Saph growls at Griffin.

Isolde hates it when people talk about her like she's not there. Like she's helpless. Or stupid. She certainly doesn't need it from two guys she doesn't even know. But she's too dizzy to protest when Griffin swings her up into his arms like she's made of fairy floss and feathers. Instead, she holds on tight and allows herself to sink into his hard chest.

"Stairs are out." Saph jerks her head towards the sweeping central staircase. It's packed with disorderly, panicked bodies attempting to surge up and out of the basement.

"Lifts won't be operating during an emergency evac," Beck points out. "Don't you guys have security? Bodyguards who can help you get out of here?"

"No private security on the VIP floor," Griffin reminds him. Only the club's highly trained bouncers are allowed in Infamy's basement.

"We can't even contact our team from down here," Saph confirms. "Too far underground, too much concrete."

"Where are the bouncers?" Issy asks. There isn't an Infamy security guard to be seen. Which is weird, because they're usually plentiful and highly visible.

"I don't like this." Saph verbalises what they're all thinking. "There's got to be another way out."

Beck sighs and runs a hand across close-cropped dark hair. "Follow me," he says. "We know a way."

Beck and Saph use shoulders and hips and elbows to carve a path against the tide of people moving towards the stairs, checking every few metres to make sure that Griffin and Isolde are still with them. As they move, they pass vignette after vignette of shock and fear and dismay. Issy closes her eyes against the disorientation and distress of it all, hating herself for eschewing the ugly even as her lids drift shut.

A Queen deals with hard things head on, Isolde.

Issy hears her mother's biting commentary as clearly as if she were standing in the throne room. Queen Maurelle has a formidable tongue and impossibly high expectations. Isolde excels in rarely meeting them.

It's time to grow up, Isolde. Become a ruler. Be who you're destined to be.

This time, the voice in Issy's head belongs to Nix. Beautiful, hard, demanding Nix. Nix of the doe eyes and freckled nose and oh-so-clever tongue. Nix, who Isolde thought she loved, completely and ever. Nix, who-

"You doing okay there, gorgeous?" Griffin whispers in Isolde's ear. Warm breath tickles like a spring breeze. As he pulls away –golden lion's eyes smiling down at her– Issy resists the urge to run her finger across the tiny mole that kisses his top lip.

"Just peachy." Isolde shakes her mother and Nix from her mind and focuses her attention on the boy carrying her to safety. Focuses on the contrast between his honey hair and her dark tresses; between his maple syrup skin and her fair complexion.

They look good together.

Isolde isn't naïve. She recognises Griffin for what he clearly is –an opportunistic playboy with a hard-on for the idea of hooking up with royalty. Still, there's something about this boy that makes her feel calm and safe, two feelings that often elude her.

"What the heck, Beck? This is a dead end." Saph's glaring at Beck like she wants to stab him with acid-soaked daggers.

They're in the corridor that leads to the bathrooms. The wall in front of them is emerald green and dominated by a brightly-coloured print of a dazzle of zebras.

There's no door.

Ignoring Saph and her stabby eyes, Beck firmly pushes against one side of the gilt-edged frame. The zebras slide sideways along metal tracks like they're fleeing across the savanna, revealing a neat, round hole cut through the wall. It leads straight into a tunnel made of what looks like wide concrete water pipe, lined at the base with black carpet, and just large enough for an adult male to move through at a crouch or on all fours.

This is no regulation exit, which makes Issy wonder how long it's been here, and for what purpose.

And how Beck and Griffin even know about it.

Saph takes one look at the unlit cylinder and jerks back as if she's been burned. "I can't," she mutters. Small, dark spaces are Seraphine's kryptonite.

"You can, Saph, and you will. We have to." Issy reaches out and grabs Saph's shaking fingers. "You said it yourself –if that explosion was deliberate, we were the likely targets. If it wasn't, we're still in danger. For all we know, this place is about to collapse."

Saph meets Issy's solemn gaze and nods, her expression a typically Seraphine combination of trepidation and dogged determination.

"It's safe, I promise," Beck squeezes Saph's shoulder. "I'll go first. Seraphine – you and Isolde follow. G –close the door behind you. If someone is after Isolde and Seraphine, we can't afford to risk them following us. You guys need to stop at any point, sing out, but the quicker we can get out of here, the better." He crouches down to enter the tunnel.

"Wait." Saph shrugs off her purple and blue silk, floral backpack and removes two rolled up balls of leather and rubber – one black, one silver. Understanding Saph's intentions as clearly as if she'd spoken them aloud, Issy wriggles out of Griffin's arms and kicks off her crystal-encrusted stilettoes, swapping them for the silver ballet flats. Saph slips into the black ones. Two pairs of heels disappear into the backpack, before it's re-zipped and slung over its owner's shoulders. The whole process takes less than thirty seconds.

Griffin mutters something about the inexplicability of women. Beck just raises his eyebrows before disappearing from view.

"You sure you're okay, Iss?" Saph whispers.

A firm "Get in the tunnel, Saph" is Issy's only reply.

With a heavy sigh, Seraphine grits her teeth and follows Beck into the dark unknown. Isolde knows what it costs her to do so, and her chest clenches with affection and gratitude for her feisty, pain-in-the-arse baby sister.

Once they're all in the pipe, Griffin pulls a small lever just inside the entrance and the painting silently slides back into place. The resulting dark is so absolute that even Issy finds it eerily oppressive. Saph's breathing drifts into shallow and ragged. Isolde opens her mouth to offer reassurance but Beck beats her to it.

"If you aren't safely out of this tunnel in thirty minutes, you can put me in jail, I promise," Beck tells Saph. "But no groping my butt in the dark and pretending it's because you can't see it."

"Shut up."

"Make me."

Saph growls but Issy can hear the begrudging amusement in her voice.

She doesn't hate this guy. That's a first.

The pipe's soft carpet lining allows them to make swift progress through the long, meandering tunnel. The cut on Issy's head stings like a mother fudger but the throbbing in her temples is easing and she's starting to feel less like life is being conducted in a thick fog.

To give herself something to focus on, Issy counts minutes in her head. She gets to twenty-two by the time Beck calls out for them to halt.

The distinctive scrape and squeal of metal on metal tells of a bolt being pulled back. As the heavy hatch door starts to swing outward, a crescent-shaped sliver of murky light breaks through the pitch darkness and quickly blooms in an arc.

"Mind yourselves on the ladder," Beck instructs. "It can be slippery."

One-by-one, they exit the tunnel into a narrow vertical shaft and begin to climb. Overhead, the gibbous moon hangs steady, bright and sure.

Issy tries not to focus on the slipperiness of the ladder rungs or the fact that the shaft heads straight down as well as up. Instead, she fixates on the probability that Griffin has a perfect view of her trusty, granny-style, 'no VPL' knickers.

Mental note to self. Order better underwear. Or wear pants more often.

"I quite like the granny undies," Griffin whispers in the dark.

"Shoot, did I say that out loud?"

"You totally did."

"Less flirting, more climbing," Saph grumbles from above.

"Make me." Griffin whispers so that only Issy hears him, with enough joking sarcasm to make it clear he's impersonating Beck.

Issy bites back a smile.

At ladder's end, they emerge into a poorly lit urban street in an area of the city Isolde isn't familiar with. Rundown, single fronted terraces share space with a crumbling bluestone church and a park so tiny it barely counts. A single red swing hangs listlessly, one detached chain dragging sadly on the pitted asphalt.

Nearby, a dog barks loud and deep. Isolde and Griffin both jump at the sound. He catches her eye with a rueful grin. She returns it.

While the boys return the metal grate to its original position over the shaft, Saph quietly unzips her backpack.

"What the actual fuck?" Beck asks as he finds himself eye-to-eye with Saph's not-so-friendly-looking Glock.

"Saph, is this really–"

"We don't know these guys, Iss. For all we know, they planted the bomb."

"You, Your Royal Highness, have really piss poor manners, you know that?" Beck sounds more frustrated than angry or scared. "We just saved your pretty princess arses and your version of gratitude is pointing a gun in my face?"

"You 'saved our arses' using a hidden tunnel that led us straight to The Wall. Excuse me if I don't think that screams 'nice boys, good intentions'."

At the mention of The Wall, Issy spins on her heel. Sure enough, beyond rooftops and straggly trees and wonky streetlights and an antique billboard advertising laundry soap, looms the concrete wall that has surrounded the city for the best part of eighty years.

Four stories high and three metres thick, reinforced with steel and topped with barbed wire, The Wall represents different things to different people. For scholars, it's a lasting reminder of how the great pandemics of the last century changed the course of history and re-cut the fabric of society. For those who live within its embrace, The Wall represents security and health. For those dwelling on the other side, it speaks to exclusion, elitism, and inequity. For Issy and Saph, its current proximity is sobering. They are a long, long way from the safety of home.

Up until this point, Issy has been cocooned by a misty haze of shock and mild concussion. The bomb blast, her injury, crawling through weird tunnels with pretty boys – all things she has pretty much taken in her stride.

Not so, the nearness of The Wall.

Without a second's hesitation, sweet, decorous, seemingly delicate Isolde, reaches into Seraphine's bag and pulls out her own handgun and a handful of zip ties. She trains her Glock 36 on Griffin with steady hands and sharp eyes – shared smiles and banter forgotten, golden boy loveliness rendered entirely irrelevant. The zip ties are thrown at his feet.

When it comes, her voice is steel-coated and not at all flirtatious.

"Tie yourselves up. Wrists and ankles. Then you both have five seconds to convince us you aren't a threat, or I start taking out kneecaps."

"C'mon, gorgeous girl," Griffin cajoles. "Be reasonable."

Without taking her eyes from his, Issy shoots the ground two inches from his left foot.

Griffin wisely reaches for a zip tie.

Beck follows suit.