A small Fiat, faded blue paint, up on the footpath down near the railway tracks, smoke or steam pouring out from under the bonnet. One flat tyre.

And birds – dead and dying birds everywhere.

A woman in a bright floral headscarf, cowering in the doorway of an empty boarded-up shop, shielding what looked like a child with her body.

Across the road from her, a dirty white van, parked at a slight angle in the gutter about fifty metres away, cabin door slid open. One leg hanging out of the interior, twitching. Windshield smashed, horn blaring.

Three identified shooters there. All white males, dressed casually, armed with FAMAS G2 assault rifles. One behind the van – possible leg wound. One crouched behind another vehicle, a grey, ageing Volvo. The last man, running, aiming for a deeply recessed doorway fifty yards away.

She snapped off two quick bursts at the figure heading for the doorway.

G2 rounds crashed around her once more, pulverising the ancient red brickwork and forcing her to fire blind again. Caitlin emptied the rest of the Steyr magazines with much greater accuracy this time, however, having sighted her targets, then she turned back into the building and shoulder-charged the first door on the right. It gave way with a crack of splintered wood and she tumbled into the small sitting room, taking cover below the window ledge, crunching broken glass under foot.

In one quicksilver motion, Caitlin slipped off her backpack and poured half a magazine of 9 mm hollow-point from the Glock through the smashed windowpane into the street outside, mostly aimed at the shooter behind the Volvo – the closest, easiest target. Chances of nailing him were low, but she could at least keep the fucker bottled up.

Monique moaned loudly just outside the room, and glancing back over her shoulder, Caitlin saw her legs begin to scythe and kick in reaction to the burning pain that would now be making itself felt. Gut shot by a military assault rifle. There was gore and leakage everywhere. Caitlin knew the exact location of a couple of morphine syrettes in one of the bags, but to attend to Monique now would have meant ceding the initiative to their would-be killers.

She opened her oversized hold-all and pulled out the artillery. The pistol-grip Benelli shotgun came first: customised 12-gauge, extended mag with a side-saddle shell carrier. Next was the deal closer, a specially cut-down Heckler amp; Koch UMP.45, with an extended box mag housing thirty rounds of.40-calibre Smith amp; Wesson goodness. She slung the HK over her shoulder. It was a large, excessive arsenal for just one young lady to haul around, but Caitlin Monroe very much adhered to her daddy’s rule that when it came to guns it was always better to have ‘em and not need ‘em than the other way around.

She picked up the shotty, jacked a cartridge into the chamber, and poked the muzzle out through the shattered window. The Benelli was loaded with a buck ‘n’ ball combo that gave her a nice spread for quick and dirty area clearance, but still packed a nasty surprise in the form of one larger, molybdenum disulphide-coated brass slug at the centre of the load. Unlike softer malleable rounds, it was armour piercing and would slice through a car door or ballistic vest without bothering to slow down much.

She methodically pumped half-a-dozen rounds of buck ‘n’ ball down-range, angling to do some damage to the men behind the vehicles, but occasionally raking a shot along the front of the building to shut down their partner in the recessed doorway. She briefly heard a few distressed cries and more shouting upstairs, and the hammering of feet on bare wooden boards, but then the uproar of her sustained gunfire drowned out everything else.

I need to get a handle on this fucking mess, she thought. She was still firing blind, however, attempting to disrupt the flow of her opponents’ advance and hoping for a lucky hit.

The briefest of lulls drew her attention upwards again, to the sounds of renewed panic. Caitlin let loose out of the window with another four shells from the shotgun and then ran, reloading, clearing the ruined sitting room and bouncing off the slimy, plastered wall of the apartment’s main corridor. She leapt over Monique, who was writhing and crying pitiably – ‘Hold on, baby,’ the American muttered, ‘these fuckers are gonna regret getting out of bed today,’ before speeding towards the staircase, slipping the shotgun over her shoulder and bringing the Heckler amp; Koch into play.

Bounding up the stairs she swung around at the first level and raced for the front of the building. An open door led onto a small bedroom just ahead and she rushed in, grateful to find there was no baby in the cot that was pushed up against one wall. She thumbed the selector on the machine-gun to full auto. One of the reasons she liked the H amp;K was its relatively low rate of fire, a modest 600 rounds per minute, which, in the hands of an expert operator, made the burst mode all but superfluous.

Caitlin looked out the window with a black widow’s smile. Two of the three shooters were crossing the road, giving her a clear line of fire. ‘Thank you, gentlemen,’ she said. ‘Much obliged.’

The operatives both squeezed off covering fire at the groundfloor position she’d just left as they crossed the Route d’Asnieres. The dense, rapid crack of their FAMAS rifles was painfully loud. They edged forward, right into her sights.

Her movements were quick and machine-like. One sharp pull on the trigger shattered the bedroom window, and as the two men instinctively looked up, she nailed the pair of them with short auto bursts, aiming for the centre mass and letting the muzzle drift upwards to punch a couple of rounds into each of their skulls.

The first man simply looked surprised, his eyebrows raised comically and mouth a perfect ‘O’ shape before five rounds stitched him up from the sternum to the forehead. His head all but disintegrated. The second attacker was fast, well trained – but doomed. He managed to lift his muzzle up a few inches, and even squeezed off one misdirected round, before Caitlin nailed him in the same way. A fan of blood and brain matter painted the side of the car next to which he died.

One more. There’s one more, at least, she screamed silently at herself.

She didn’t pause, instead leaning back from the exposed position and holding the gun forward, angled down, to let rip at the guy who had been sheltering in the doorway. There was no direct line of sight, but Caitlin fired from memory, confident she could at least keep him pinned down. A woman was screaming nearby, and downstairs she could hear Monique’s guttural cries of pain becoming more ragged and intense, more animalistic in their abandonment.

‘Shitfire!’ spat Caitlin.

She took half a second to scan her immediate surroundings and plug them into a larger mental map of the world outside. A triangular block, typical of the streets of Paris, was her battlefield. Time to slip backasswards.

Setting off at a sprint, she exited the room and charged down the first-floor corridor – a dank, evil-smelling space. She headed away from Monique, away from the cries of the tenement’s occupants, moving as fast as possible for the rear of the building. A closed wooden door loomed ahead of her, and she went straight through it, shoulder-charging the old frame, which disintegrated in a storm of splinters and dust. A faraway part of her mind thought, Termites.