A/N Hi this my first story. I am going to be sticking to the films and books as much as possible but changing it occasionally to make it fit. This is going to be a Percy Jackson/Avengers crossover so I will say it now. I own nothing. All rights go to Marvel Studios and Rick Riordan. Pairing of Percy x Natasha. Anyway on to the story. It takes place just after the end of The Heroes Of Olympus Series. Anyway hope you enjoy!

Prologue : Budapest

Nobody's POV

It was a beautiful winters day in the Hungarian Capital, snow covered the ground like a crisp linen sheet. The sun shone down on the grand buildings of the city illuminating them radiantly against the clear blue sky. People went about their day not paying attention in their rush to get to work or complete the chores of the day but if had you looked closely at the shadowed areas in the tightly wound cobbled streets you would notice the red headed woman who blended in with the shadows as if they were apart of her. The woman raised her wrist to her mouth and begin to speak in a hushed voice.

"Clint, you there? I am almost in position." she asked?

The woman could hear a few soft grunts and bangs coming through the tactical earpiece she was wearing. "Just a minute!" he shouted before a few more crashes could be heard before finally the man identified as Clint spoke again as he wheezed out of breath. "Almost there Natasha ran into a bit of trouble." Natasha chuckled at her partner's poor fortune. Snapping quickly out of her thoughts she cut the connection before briskly making her way on, her steps soundless as she moved through the inch high snow. She was about to round the corner when she forced herself flat against the wall not a moment too soon as a second later a patrol of guns for hire dressed all in black carrying high powered M4 carbine rifles strolled past her.

The air was tense as she got nearer to her objective. A terrorist who had connections to HYDRA called Vincenze Garchinski. She had memorised his image from the case file. He was imposing to say the least standing at 6'3 with bulging muscles, a scar ran the length of his face and he had a cruel sneer plastered on his face. He was holed up in an abandoned factory just inside the capitals borders on the edge of the city.l the problem was he was untouchable by the Hungarian law enforcement as he had payed off half the officials in the government. Stepping out from the wall she peeked her head round the corner before letting out a breath she didn't know she was holding, seeing the coast was clear took off at a steady pace down the street. Turning the last corner she set her jaw at the mercenary that was glaring at her. He smiled showing off a set of blackened teeth, a semi automatic pistol which he had gripped in his beefy hands was leveled at her.

"Freeze. Hand up, behind you now." he said in broken english. She did as she was told and slowly lifted her hands behind her head, he broke eye contact for a second to radio for backup touching the walkie talkie strapped to his shoulder. Luckily for her one second was all she needed because as soon as his eyes left hers she pounced and swung her foot out sweeping his legs from behind him aiming a well placed punch to the side of his head knocking him out cold before he hit the ground. She stood up and straightened her black jumpsuit before walking over to the limp man and pulling out a silenced pistol. A soft ping could be heard as the round discharged and the man's life ended. After waiting a while on alert to make sure she wasn't heard Natasha clung to the shadows as she stalked through the dark until the path opened up into a clearing. At the end of the clearing surrounded by thick forest was the target building. A three storey tall crumbling structure that used to be a car manufacturer, but where there used to be a bustling production line now stood the base of operations for the group of mercenaries and thugs who caused chaos in the day to day lives of ordinary citizens.

"I'm in position." Clint mumbled over the radio. Natasha looked up to see him giving her a thumbs up from one of the rooftops overlooking the abandoned building his bow in hand before he disappeared. "I'm going in watch my six." was all she said before she took off at speed heading for the door of the warehouse. Listening out for any sounds Natasha placed a hand on the door before silently opening it and stepping through holding it open in case she needed to leave quickly.. The entrance was dimly lit by the sunlight that streamed through the cracks in the boarded up windows, other than the empty weapon cases that sat against the far wall Natasha decided there was nothing important here. The light from the open door crack was snuffed out as the special agent sped silently down the hallway her eyes scanning the many rooms and offices lining it.

- Time Skip -

Natasha was running out of patience. She had run around the blasted warehouse and not found a trace of anything even where she currently was on the factory floor. Surrounding her were massive stores of supplies from food and water to beds and guns but not a single merc or Vincenze himself. Stomping her foot in frustration she heard a dull thud. Immediately she snapped her neck downwards with such force anyone watching would think it would fly off. She instinctively crouched and inspected the floor with her heightened senses she could see the faint outline of the trap door and the breeze that was escaping the cracks. Tentatively she pulled on one of the cracks and the hatch opened with a shiver, soundlessly she opened it all the way. A steep staircase made its way down into the a dark stone corridor where a faint light was emitted.

"Clint I found their base. It's in the main factory floor under a hatch. I am gonna check it out." she said into her radio. Clint replied back almost immediately "Nat wait up I am coming down." With graceful steps she started to make her way down "I'll be waiting up ahead going to check it out." Clint tried to tell her to wait but he was cut off by her turning the radio off. Taking in her surroundings she noted the dim bulbs hanging from the ceiling in the long hallway. The hallway ended in a steel door and as she approached she could hear a muffled voice.

Quietly as she can she approached the door and just as she was about to open the door a rough hand grabbed her shoulder, quickly grabbing the hand she dropped into a front roll pulling the person forward before spinning un-holstering her gun and resting it against the assaillants head. What she was not expecting was the wide blue eyes of her partner meeting her cold hard green eyes. Her gun arm relaxed and the cool steel left his short cut brown hair. "Thanks for that thought you were gonna shoot me there." he laughed lightly but was cut short by her finger gesture to keep quiet. She pointed to the door and then gestured for him to take point. He nodded and got ready as she held up 3 fingers and counted.

3…

2…

1…

BANG. The door hit the other side of the wall with a crash as the occupant turned suddenly aware, he narrowly nodded the arrow that embedded itself an inch from his head. Scrambling for cover the man spoke in a rough Hungarian accent. "Ah so S.H.I.E.L.D sends their assassins to take me out. I am truly honored by your presence Hawkeye. And if you are here I assume the lovely Black Widow is here too?"

As he finished the two now named S.H.I.E.L.D assassins entered weapons drawn aimed at the cover he was hiding behind. "Id say the same but its not polite to lie in front of a lady." Clint retorted. With an unspoken agreement they both split using a pincer to move in on his sliver of cover. Just as they were about to spring their attack he jumped from his cover tackling Natasha driving his knee into her stomach, ducking quickly to avoid the arrow clint fired he rose quickly delivering a powerful uppercut that would have knocked her out had she not thrown her head violently backwards following through with the action she backflipped kicking his chin knocking him backwards into a waiting Clint who hammered on his back with his bow. He fell to the ground cursing and rolled to the side to avoid a knife wielded by Natasha. The two assassins stood side by side watching warily at their opponent who got up lazily and cracked his neck. Before either of them could blink he struck, a flurry of punches and kicks that had the two backing up further and further.

"Man what did this guy eat for breakfast." Clint said through the barrage. Narrowly ducking under a punch to find a leg sweeping his out from under him. Before he could react he felt the cold point of a knife against his throat. Natasha could only watch as he was forced onto his feet the knife point pressing against his throat. "Put the gun down Widow or he dies." To prove he was serious he dug the knife point in a little drawing a line of crimson blood to form at Clint's throat. "Nat dont do it remember the mission." But she couldn't do it so she lowered her gun reluctantly to which Vincenze just grinned evilly "You should have listened to your friend here." and before she could even move he had plunged the dagger into Clint's side. She reacted immediately forgetting one of the first rules of S.H.I.E.L.D training. Never let your emotions compromise you, but all she could see was red for this guy who has hurt her partner so she attacked viciously with a fury only attainable at seeing a close friend hurt. She thought she was making ground on him before he swatted her across the room with ease. Immediately her vision darkened as she fought off unconsciousness vicious grip. Through the haze she could see him stalking over to her looking at ease he was talking into a radio. "I have them both here. They will be disposed of soon and then we can take the experiment and leave. Everyone to me so we can move the equipment."

For one of the few moments in her life Natasha actually felt fearful of what was to happen as the loud pitter patter of feet echoed around the building above them. There was at least 20-30 fully armed mercenaries coming for them, but she couldn't help but notice what he said. Experiment? What does that mean? She was brought out of her thoughts by a rough hand yanking her up. Vincenze was inches from her face and wearing his trademark sneer. "Look at you. Pathetic. My boss is going to be pleased with this." Wait boss? This confused her even more. Through the pain she could notice a tall muscular figure behind Vincenze. "Great" she thought "His backup arrives and I can't do anything due to this concussion."

But then the man did something she did not expect. Natasha felt the pressure on her suit loosen as Vincenze was flung back by the mystery man. "You." Vincenze snarled "You aren't supposed to be awake yet. No matter. There is nothing you can do." he said as he heard the footsteps of the oncoming mercenaries. The man seemed unfazed as he walked toward him menacingly, Vincenze took a defensive stance and swung a fast swing at the man's face. A resounding crack was heard as the man's head snapped to the side before a roar of pain could be heard. Natasha's eyes widened as she realised the roar came from Vincenze who was now holding his broken wrist. With a carefree punch the man knocked the terrorist out. Doing a sweep of the room the man spotted Clint and started over to him. Natasha tried to stop him. To scream at him to get away but her voice had deserted her. She watched helpless as he picked Clint's pale form up before walking into the bathroom and leaving her there awaiting her fate. He emerged five minutes later covered in blood as tears pricked Natasha's eyes. What had he done to him? She had no time to ponder that thought as she watched the reinforcements arrive. The first through the door looked around and when he notices the blood covered muscle bound man standing over Vincenze's crumpled form he charged the man and Natasha watched amazed as he easily disarmed and disabled the man. Her vision was failing now as he disappeared into the corridor. All that could be heard were the echoes of screams of pain and machine gun fire. As her eyelids began to drop the man reappeared with a couple bullet wounds and bloodied knuckles. He rushes over to Nat and scooped her up. She looked into his face for the first time and saw a young sculpted face. Raven black hair falling over his forehead almost completely covering his eyes. They were the last thing she saw before the world faded to black. Two swirling pools of dull sea green that looked dead to the world. And then unconsciousness took her…

A/N So what did you think? Would be grateful for any feedback. Thanks in advance!