It was quiet outside, barely a sound aside from the wind whispering through the deserted buildings around them. Dust carried in thin wisps as they set forward and Junsu couldn't help sparing one last glance behind him.

The thick sheet of metal serving for their door blended almost perfectly with the rest of the building concealing their hideout, but he pretended he could still see the others inside, maybe sharing a quick joke and a laugh that God only knew they deserved. The door could only be opened from the inside and the three trudging further away from the base each had a transmitter that would signal with a harsh, constant beep to alert the ones who remained of their return.

He cast his eyes to the two men with him. The ten people that their unit had started out with had been a large group for a town of this size and was relatively unheard of. The six they now had was about the standard number. They worked in small, compact groups which was ideal to keeping movement discreet and to carry out missions effectively. It also meant they could blend in easier and it would keep their bases small and easier to protect. There also weren't enough fighters to go around.

Junsu looked down to the cracked earth at his feet as they crossed over a boundary line, then another, then another. They had marked rings of explosives in sloppy but effective circles set at one hundred, one hundred and fifty and two hundred metre radius' from their base, a standard design of protection at any military post. The security served as triple protection and also kept the base safe if the outermost boundary was set off until it could be replaced, which took a lot of time and a lot of money. Their own presence wouldn't trigger the bombs, but as soon as any Metal Heads crossed the line, sensor's would detect their unique genetic code and they wouldn't even have time to lift another paw before explosions of something similar to liquid fire would erupt along the boundary. The Metal Head that triggered the blast would be blown to pieces while those close enough would be hit by flames that at their flesh and spread like wildfire between them. The Metal Heads were simple-minded but they soon learnt to keep well clear. Junsu had seen explosions detonated on only one occasion, but the destruction it had caused left him feeling sickened; crossing the boundaries always made his stomach clench in fear and he couldn't help wondering 'what if...?' as he glanced down.

None of them spoke as they pressed further on into enemy territory; communication wasn't needed: you had to learn to work as one or risk jeopardising your lives as well as the mission.

Although it was dark, they could still make out vague outlines in the limited light of the moon and they also knew the layout of their town like the backs of their hands. Though he couldn't see it clearly, Junsu could still picture the old sweet shop with one wall, the scattering of craters left from past explosions, the dark red stain on the door of building 53 and the small teddy bear with one leg outside an apartment block as if it were broad daylight.

A flash of yellow light sparked in the darkness above a building ahead of them and Nichkhun sank smoothly into a crouch, a knee on the floor and one fist in the air. They froze. Junsu followed suit not even a second later as Wooyoung swung his rifle from his shoulder, made sure the silencer was screwed tight and took aim. The Metal Head dropped and its skull gem fell from the building, clinking as it bounced.

Nichkhun didn't lower his fist as they waited for signs of any further enemies. Deeming the coast clear, he stood and they moved on like wraiths in the night.

The closest entrance from their base to the sewer wasn't far from the third boundary, and this is the entrance they chose to use for the mission, though they often switched around to avoid Metal Heads determining where they'd hit next. They were deep in slum territory when the ramp down to the sewers materialised in front of them. They descended cautiously, weapons raised against the darkness, and waited as the cogs in the sewer's heavy iron door began to spin. For some reason, the locks on these doors would only open at the presence of a human and Metal Heads couldn't get in using this method; it hadn't stopped them finding other ways though.

The cogs came to a halt as they aligned and the doors slid apart, cool night air rushing in and forcing out the slimy air of the sewers. They tensed in case of any Metal Heads lying in wait, but the coast was clear. Nichkhun took a deep breath of the new dank air and sighed it out in mock appreciation. Wooyoung hit him on the back of the head, all three chuckling silently but without humour as they stepped inside.

Water dripped in continuous rivulets down the rough grey walls, sometimes made of metal but mostly stone, and rust had worn away part of the pipes and tunnels in some places, especially in the old unused system where they were headed. Some tunnels and pipes had caved in, either from the shock of explosives or work of the Metal Heads, and it meant they often had to keep check of dead ends and edit the map they kept in their heads.

They fell into formation as they moved forward, Nichkhun in the lead with Junsu and Wooyoung fanning out to either side two paces behind him. Their weapons were always ready and their torches were out in case the small, flickering lamps in the ceiling died or had been smashed out since their last visit. Junsu saw the large white stain next to a grate in the wall a turn away from where they entered. He always noticed it and would feel his spirit rise when he saw it on his way out; it meant daylight and fresh air and almost-safety.

They managed to move forwards stealthily and without incident and they soon reached the first location. It was a T-section of tunnel, the path branching off leading to an unused section of pipes in the sewer network. Past expeditions into the sewers had revealed a lot of Metal Head movement around this part of the system and they couldn't let it continue, especially if the Metal Heads were using it as a refuge. Thankfully there were only two entrances left as others had either caved or been filled in long ago.

Nichkhun crouched and set to work laying explosives on both sides of the entrance frame, Junsu and Wooyoung covering him as he worked. Junsu had no worries with Nichkhun's skills; it was what he was best at. They all took great care in keeping silent; if the Metal Heads were indeed moving in the pipes, they would definitely be heard at such a close range.

Standing and backing away carefully, Nichkhun waved them forwards. They crept vigilantly on, returning to formation, and followed the tunnel straight until they had to navigate an arrangement of ledges. Junsu breathed deeply as he climbed and he didn't look down when he had to jump two metres over a hole with no discernible bottom.

Three turns away from their final destination, Nichkhun held up his fist again, and they could all hear the sound of scurrying around the next corner. Making motions with his hands, the three edged forwards then charged around the bend, hoping for the element of surprise.

Three Metal Heads scampered around in the tunnel. They were the kind that looked like scorpions and were no bigger than the length from Junsu's elbow to the tips of his fingers, including their stinger. They were the weakest type of Metal Head, relatively easy to kill and the stinger wouldn't do any permanent damaged (as long as it didn't go too deep into your torso), though that didn't mean it didn't hurt. Junsu knew that they'd all found that out at some point or other, none of them having been quick enough to dodge a stab when one dived from the shadows or from beneath an open drain filter.

Three skull gems were dislodged and bounced away as their bullets hit home; they rolled into a pool of stagnant, waist deep water that Nichkhun immediately jumped into.

Skull gems were slimy to hold, about the size of Junsu's whole hand, and were somehow ejected from the skull after death; they continued to shine with light and never went out. At first, people thought they might be the Metal Head equivalent of a brain and that they would be able to extract information. They'd had no luck and the skull gems had no use at all (that they'd found so far, at least) but some liked to collect them as trophies of their kills.

Wooyoung and Junsu followed suit, wading forward and trying to ignore the shivers from the cold water and whatever else might be floating in there. A wet path followed them around the last two turns and they finally reached the last T-section.

Keeping their eyes and ears open for any sound of movement, they waited as Nichkhun did his job. Everything went smoothly until scuffling echoed down the tunnel from both directions. Waving his hand around in the air and keeping his eyes fixed on his beloved explosives, Nichkhun signalled them to check it out, knowing he'd be okay for the time being, and Junsu and Wooyoung nodded to each other before taking off.

Junsu followed the path back along the way they came, body ready to spring at any sign of movement. A small tunnel branching off to the main network caught his attention but after no further noise he was about to move on, until a quiet scraping reached his ears. Shining his torch in the direction, he held his breath when he noticed a wall grate hanging slightly open. Inching forwards, he readied his finger on the trigger and flung the grate fully open, his torch illuminating the pipe.

A man cowered inside, his hands trying to block the bright light from his eyes. Junsu stared in shock, a man being the last thing he expected to see. He lowered the light slightly, but not his weapon.

The man's face and hands were grimy, streaked with dirt and God knew what else. His hair was short and matted and dark eyes, even smaller than Jaebeom's, stared back at him. He looked terrified, lost, alone, broken.

"Who are you?" asked Junsu, trying to push aside the look in the man's eyes.

He didn't answer, but he did lower his hands.

"What's your name?" No answer. Junsu looked him over again and this time noticed the torchlight glint off of dirty gold thread sewn into a word on the pocket of the man's dirty shirt. "Junho? Is that your name?"

Junsu lowered his gun when the man still gave no answer and waited to see if he would attack. He continued cowering but nothing more. Reaching in, Junsu grabbed his shoulder and pulled him from the pipe. "Come on. Let's get you out of here."

Despite his fear, Junho still had enough sense to follow and let himself be dragged back to Nichkhun and Wooyoung. The other two were already returning back down the tunnel, Nichkhun's job obviously finished and Wooyoung with a splatter of dark red marking his cheek. They stared in shock, much like Junsu had, for a brief moment before taking Junho's arrival in their stride: it was shoot first and ask questions later when you've managed to survive for at least another hour; you learnt to follow that rule pretty quickly.

Wooyoung led this time, taking them on a detour that would get them to the exit fastest from their current location and would also let them avoid the pool and the hole in the floor. Nichkhun hung back and helped Junsu keep Junho in step with them; everything was obviously a shock to him and his legs didn't seem to want to follow.

Almost out, they were suddenly forced to stop at a loud sound of scrabbling against metal. A second later, a section of weak ceiling collapsed and a Metal Head crashed through right on top of Junsu. He barely had time to shout before he fell back with it on top of him, his head colliding harshly with the ground.

Its body was jagged with broad shoulders and solid natural armour covering its shoulders, elbows and calfs. Its skin was a deep blue and its teeth matched the sharp claws on its hands and feet. It was one of the bigger ones he'd seen.

Junsu gasped under its weight, his head still reeling from the impact, but he wasn't allowed time to recover. The Metal Head grabbed him by the throat and lifted, swinging him round to slam him against the wall. His head snapped to the side from the force and his eyes locked with Nichkhun's then Wooyoung's. Through the haze of pain he could see goodbye in their eyes. He understood. It was too dangerous for them to stay and he knew that the rule that had been drilled into them in training would be ringing through their heads: Fall behind, left behind. In this situation, it's what you were taught.

Junho stood horrified next to them, eyes wide and mouth open. Wooyoung and Nichkhun each grabbed an arm and tried to pull him along but he struggled, staring at Junsu, until Nichkhun shouted in his ear. "Follow or we leave you!" It snapped him back into his body and he let them drag him up the tunnel, turning his head to look back at Junsu all the while.

Junsu knew it was the end. Metal Heads were too strong once they got a grip on you, especially one of this size, and there was nothing to be done. The Metal Head roared in his face and grinned maliciously, obviously having the same thoughts as Junsu. Junsu closed his eyes and he briefly wondered if Jae would send them to retrieve his body like they had with Kwon and Seulong, or if the Metal Head would drag him away like Changmin and Jinwoon.

He waited, the Metal Head's hot breath at his skin, when the first of the bombs went off in the maze of tunnels, the vibrations so strong that Junsu's head bounced lightly against the wall. The Metal Head snapped its head towards the sound, momentarily distracted, but it was all Junsu needed. Digging deep for as much strength as he could muster, he brought the heel of his palm into the Metal Head's chin. Its grip had loosened through surprise and it was knocked off balance and took a few steps back, dropping Junsu with an angry snarl on its lips.

Legs nearly crumpling beneath him, he immediately reached back for the handgun in the waistband of his trousers; he had no time to marvel at the luck that it didn't get knocked loose.

The Metal Head had already recovered and had dropped to all fours, obviously displeased at its loss of executing an easy kill. It prowled back and forth in front of him and began circling, rumbles sounding angrily in its throat. Launching itself forwards, Junsu knew it hoped to catch him off guard, but he was ready for it; they'd learnt to use an opponents weight against them in training. Rolling back with it, he attempted to slam it down on its back. He succeeded, barely, but its claws still sank into his arm and tore messily at his flesh. Ignoring the pain, he tried to pin it down. It snarled once more and tried to strain upwards, no doubt with the plan of sinking its teeth into his throat, but he placed the barrel of his gun inside the gaping cavern, shut his eyes and pulled the trigger. The skull gem tinkled as it skittered away.

Opening his eyes, he stared down at the Metal Head for a second, the slimy sewer air now tasting like fresh lungfuls of sweet oxygen. He didn't linger and there was no time to rejoice: the next bomb was soon to detonate and the first explosion, as well as this fight, would no doubt have attracted attention. He hadn't survived yet.

Staggering up onto shaky legs, he jammed his gun back into his waistband and collected everything that fell in the fight, nearly slipping on the skull gem as he slung his rifle back over his shoulder. He kicked it away up the tunnel, knowing he had to collect his wits and keep his head clear if he wanted to get out alive, as he took off after the others, his legs immediately on auto pilot as he tried to ignore the collection of growls echoing up the tunnel behind him. He knew they were still far off and that the sewer's echoes were magnified, but that didn't mean his heart didn't jump in fear.

Around two more corners he ran past the white stain he always took note of upon entering the sewer and he knew he was only one more turn away from the exit. The cogs were slow to turn and he had to fight to resist hammering on the door to hurry it up. "Come on come on," he muttered, squeezing through as soon as the opening was large enough. Daylight stabbed at his eyes and he knew he couldn't stop, not yet.

As he was climbing the ramp, the second explosion went off, seeming to shake the earth to its core. It was right on time: glancing up at the sun he could tell it was in the ten o'clock position; it had been seven hours since they had left that morning. Junsu just hoped the plan that the daylight wouldn't matter would hold true. They intended on the Metal Heads being distracted by the explosion and it also paid off to shake up their mission times so that the Metal Heads never knew when they'd strike.

He sprinted back through maze of streets and alleyways, returning back past the one-legged teddy bear, the red stain and the craters. It wasn't until he reached the single wall of the sweet shop that he heard a crash behind him. "Oh no," he muttered. He was still over a hundred metres from the first boundary line and the streets were still winding. Glancing back over his shoulder, he spotted a Metal Head about fifty metres away, leaping from building to building as it prowled towards him. Pulling his rifle from his shoulder, he jogged backwards and tried to take aim. The Metal Head barely dodged the hail of bullets. Snarling, it started forward again only to be thrown back by a well placed bullet between its eyes.

Slinging his rifle back over his shoulder and glancing down at his handgun that had saved his life twice more today, he whispered a "Thanks baby" and kissed the barrel before returning it to its place at his back.

More were coming. He could hear them.

Weaving through streets he kept giving fleeting looks over his shoulder. He could spot three Metal Heads scaling the buildings in the distance but he knew there would be more: skull gems weren't so noticable in daylight and camouflage wasn't so difficult in a city as ravaged as theirs.

The first boundary flew by under his feet but he didn't slow despite the higher level of safety; he knew they couldn't get in though he still worried that they might try.

He reached the second boundary.

Then the third.

The door of the base grew larger ahead of him. He could practically hear the beep his transmitter would be triggering. He'd made it. Sprinting the last few metres, he stretched out his arms, ready to push it open.

A second later, he slammed into the solid metal, his head cracking heavily against it. He was thrown back a few paces, a lump surely already forming from the impact.

He stared, mouth falling open as he began gasping for breath, the long dash taking its toll.

"No," he whispered, rising to a shout. "No no no!" He tried again, shoving, bewildered as to why it wasn't working. His stomach went cold, like he'd just swallowed a glass of ice cubes, in realisation as he stared down at the wound the Metal Head had given him in their fight. Blood was running down his arm in thick rivulets and his shirt sleeve was in tatters.

Right where the transmitter should have been strapped to his skin.