Author's Note: Hey everyone! So, I've had to take a really long break from writing due to my SUPER busy schedule. Applying to schools, taking classes and getting good grades, the whole thing. I'm trying to get back into the swing of my regular writing routine, so I decided to go to a Supernatural prompt blog (user destielficprompts) and write a short fanfic based on an idea I liked. This one was submitted to them by tumblr user lamppu. The prompt is too long to write here (it was basically an outline for an entire story!), but the gist was that Cas would end up in the past and would interact adorably with an infant version of Dean, with Mary wondering what their connection was.

In terms of the time, this should take place somewhere after Holy Terror (9x09), with the Winchesters and Cas out on a hunt. I'd like to imagine they're all living at the bunker together in this one.

Anyway, this is getting far too long, so on with the story!

Disclaimer: I do not own Supernatural or anything affiliated with the CW.

"What the hell is this thing?!" Dean yelled, stumbling back from the powerful punch the monster plowed into his stomach. It was the worst hit he'd ever taken; more than the wind being knocked out of him, it was like all of his energy had been sucked away, fed on by the creature. It was awful. He collapsed onto the cold, hard floor, his spine striking painfully against the concrete. His head smacked back, and he stared, dazed, up into the fluorescent lighting of the warehouse. A few feet away, Sam yelped as the monster grasped his shoulder, a small blue light transferring from him to the creature's hand. "Sam!" Dean cried out.

Sam heaved up the heavy metal bar he was holding and smashed it into the thing's head. It released him, howling in pain and clutching its skull. Sam fell to his knees and gripped his upper arm, trying to catch his breath. He closed his eyes and called behind him, "Cas? What are we facing, here?"

On the other side of the room, the angel was having no better luck than the brothers. The third monster had him in a choke-hold, and was drawing the same blue light from Cas' neck. His eyes rolled back into his head, and the hand holding his angel blade went limp.

Dean sat up and looked behind him when his friend was silent, then jumped to his feet as soon as he saw that he was in peril. "CAS!" he shouted, grabbing his gun from where he'd dropped it and running over to the opposite end of the warehouse. He lifted the weapon into the air, aimed, and shot the beast straight in the chest. It released Cas, who fell to the ground and began coughing up blood and pounding his chest.

"I believe I know what this is!" Cas called out hoarsely, rubbing his throat. "Though I can't recall its name, I know that it feeds off of a human's energy. It will literally suck the life out of you." He turned to the others. "In mortal danger, it will send its opponent back in time for roughly thirty minutes, while time continues on in the present. During this time, it feeds on you from afar, and once the time is up, you die, unless you can find some way back to your own time."

Sam shuddered from his place on the floor. "That doesn't sound like fun," he muttered under his breath.

The sickly being turned it's attention to Dean.

Dean pulled the trigger again, but – of course – it was stuck. Great. Just my friggin' luck. He looked around hurriedly for something, anything, to help him against this thing, but there was nothing in sight. Gulping, he took a few steps back, his eyes racing in every direction. This is it. This is where it all ends. The monster was only a couple of feet away at this point, reaching out to him, trying to touch him -

Cas threw himself in front of Dean, holding his angel blade out in front of him as if it were a sword. The creature cowered back and shot a brilliant white light at him. The light swirled around Cas, circling its prey, then encapsulated him, before bursting around the room, showering everything in the brightest shine in existence. Dean shielded his eyes; it was like staring into the sun. After a few moments, however, the room returned to normal, and Dean pulled his arm away from his face. Only two of the three monsters were huddled together at the far end of the room, Sam was still on his knees nearby, and Cas was -

Not there.

Dean look around wildly for his best friend, but he was nowhere to be seen. Shit, Dean thought. Shit, shit, shit.

This meant only one thing.

Cas was going to die in thirty minutes.

A cold rush of wind whipped his face, bringing him back into consciousness. He let a moan escape from his lips; his head felt like it had been hit by a pile of bricks, and his body ached all over. His sore muscles protested even when he tried to move a mere INCH. These human bodies are so fragile, he thought in frustration. An injury like this would barely hinder my true form.

With a sigh, Cas slowly cracked open his eyes, taking a moment for his pupils to adjust accordingly to the velvety night sky. With a grunt, he placed his elbows on either side of him and heaved himself up into a sitting position, ignoring the pain in his vessel's abdomen. He groaned again, rubbing his temples with his fingers. Later, he'd have to ask Dean what the cure was for headaches. Though the grace inside him technically made him an angel again, it did nothing to prevent him from obtaining physical injuries, as well as from death.

Which meant that, if he could not find a way out of whatever time period he was currently in, he would die very, very soon.

Slowly, he climbed to his feet and surveyed his surroundings. He seemed to have landed in the middle of a park; the ground beneath him was shaped into a long, winding path, and he was surrounded by grassy hills and trees. If he listened hard enough, he could just make out the hoot of an owl.

He glanced behind him, searching for some sign of which way to walk to find the exit. Unfortunately, only pure darkness lay in both directions. He sighed, then started walking forward, hoping to meet someone along the way (though his rationality told him that nobody would be in a park this late at night). After a few minutes, however, he spotted a young woman on the curb, walking a small puppy. With her other hand, she clutched onto a stroller that held an infant.

Cas approached her. "Hello?" he called once he was several feet away. Her head shot up, making her blonde, wavy hair bounce, and she began to turn around. "Ma'am, I was wondering if you knew-"

Cas stopped short, blinking a few times, and felt shock course through him. He couldn't believe what he was seeing. Was this merely a coincidence?

The woman stared at him, puzzled. "Yes...?" she questioned, her brow furrowing.

Cas' eyes shined, and he smiled just slightly. "Mary Winchester..." he murmured in wonder. He closed his eyes and inhaled deeply, saying a small thanks in case his Father, or anyone else, was listening.

Mary continued to stare. "Do I know you?" she asked, her face blank.

Cas quickly shook his head. "No. Well, you shouldn't, anyway." He reached down and took her hand, shaking it emphatically. "You were a hunter, correct?"

Mary's eyebrows lifted sharply. "Who wants to know?" she whispered, her voice steely. Her mouth formed a deep, stern frown. "Because I'm not anymore. That part of my life is done. It's over. I've moved on. Do you understand me?" She took a step closer to Cas, staring him down.

Cas clenched his teeth in frustration. These headstrong Winchesters, he thought in annoyance. "Yes. I know. But time is running out, and I require your help immediately. It will not take you long, and then you may return to your life." He gazed at her, his expression serious.

Mary folded her arms. "I have no idea who you are," she pointed out. "You could be a demon for all I know. Or a psychopath."

Cas ripped off his coat and spread his arms wide, like Dean told him to do when he was in this type of situation. This was apparently protocol when testing to see if a hunter was trustworthy. "You can pat me down and toss holy water on me, if you like. I'm not carrying weapons, and there won't be any smoke," he recited from memory.

Mary glanced him up and down, then opened her jacket and pulled out a small vial of the liquid in question from an inside pocket. She unscrewed the cap, took another step forward, and poured it over Cas' head. Her mouth quirked to the side, and she quickly gave his pockets a few short pats before walking back and nodding her head. "Okay. You're clean."

Cas exhaled in relief. "Thank you," he said sincerely, picking his coat up off the ground. "And my name is Castiel," he added.

Mary peered at him expectantly. "Castiel what?" she asked when he remained silent.

Cas started in surprise, then cursed himself for not coming up with a last name. "Castiel..." He searched his mind as fast as possible, then settled on the first thing he thought of. "Novak." He cleared his throat. "Castiel Novak." He tried to look honest (something Sam had informed him he was bad at, though he disagreed).

Mary tucked her hair behind her ear. "Castiel Novak," she repeated. Cas nodded. Mary pinched the bridge of her nose and sighed. "So, what's your problem?" she asked reluctantly.

"I'm from the future, and I was sent back in time during a fight with a supernatural being that is unknown to me," he stated bluntly. "It's currently feeding off of my life energy, and, in about 25 minutes, it will be done and I will be dead. I need to know how to get back to the future and, subsequently, defeat it." Though he'd heard of their existence, this, unfortunately, wasn't one of the creatures he'd known in great detail during the course of his time in Heaven.

Mary blinked. "Okay..." she said slowly, digesting the information. "And how do I know you're not just some crazy person? Huh? How do I know you're telling the truth?"

Cas pressed his knuckles against his forehead in exasperation. There wasn't time for this! He needed her help now if he wanted to figure out a way to get back to Dean and Sam before he died. He wracked his brain for an idea, some way to show her that he wasn't lying...

Suddenly, his eyes lit up. That's it! He dug in his coat pocket for the old photograph he kept of the brothers whenever he was away from them. He'd collected it one day just over three years ago; it was lying on their hotel room desk, and was from before their father died. When he questioned it, Sam had explained that they were in a bar and Dean had just won his third pool match in a row, earning him $200 dollars. Sam decided to take a picture to celebrate the occasion. What was useful about the picture, however, was the fact that Dean was wearing John's leather jacket.

"Here," Cas grunted, handing Mary the picture. She took it cautiously, then looked down and studied it carefully. She gasped. "That's my husband's coat!"

Cas closed his eyes wearily. "I know."

Mary's hand flew to her mouth. "Who is this in the picture? Who's wearing it?"

"Your son."

Mary looked stunned. She glanced back to the baby in the stroller, then returned her focus to the man before her. "My Dean?" she asked, bewildered.

Cas nodded.

"Wait," she said, her voice cutting through the air like a knife. "If you're a hunter, and you know Dean in the future...does this mean I raise him to be one too? Why would I do that?" She sounded fearful.

Cas opened his mouth to confirm her theory, but stopped short when he saw her expression. Though he still didn't quite understand the different human emotions, his time as one of the beings made him realize that he must take a person's feelings into account when talking to them and adjust his replies accordingly. He tried to think of the situation from her point of view: almost losing her husband to a demon, hating her life as a hunter, finally getting away from it only to discover that her child would somehow end up involved in it. He gazed at her, feeling his heart go out to the poor woman. The idea must cause her a lot of pain, he realized, and felt a sudden rush of sympathy. Well, I won't let her find out about the future. Not this time, he decided, setting his jaw in determination.

"No. Absolutely not," Cas lied. Mary's face flooded with relief, and Cas was glad. "We - we have the same day job," he continued. "I just...hunt on the side. But I knew you used to be a hunter, so I was very glad to find you here."

Mary smiled slightly. She took a deep breath. "Well," she started, "I suppose it won't cause much harm to help you out with this one. After all, it's not like it's a real hunt. It's just research."

"Yes, that's all," Cas agreed. "There's no danger, I can assure you." All of a sudden, he felt his heart begin to beat at an accelerated rate, and he doubled over, gasping. Numb. Everything was numb. He couldn't think, couldn't feel anything but the numbness. And the pain. The excruciating pain. He squeezed his eyes shut, hoping and praying it would leave him alone, until he felt a sharp tug on his chest, forcing him to look down.

The blue light was being pulled from his heart.

He held his breath and stared at it, mesmerized. After what seemed like forever, it finally stopped, and Cas shook his head to get his bearings back.

Mary looked at him, terrified. "What was that?"

Cas' gaze fell to the ground in dismay. "My life being sucked away. I'm running out of time. Please, say you'll help me," he pleaded.

Mary surveyed him one more time, then finally nodded. "Okay. I'll do it. Let me just drop Dean off at home and get Lila here back to her owner's house," she said, gesturing to the small dog.

Cas smiled gratefully and fell into step beside her. I hope Dean and Sam are okay in the future, he thought nervously. After all, time is still passing for them.

Author's Note: That's all for now, folks! This is going to be super short (only about three chapters), so the next one should be up sometime this week. I know that there's no such thing as the monster described in the story, but I was too lazy to find an actually mythological creature that fit the bill, so you're stuck with the one I came up from my imagination :P Sorry about that. But considering how tiny fic is, I don't think it's that big of a deal. I've also taken some liberties with canon in terms of Cas' ingested grace (the one he stole from another angel), but they've never explicitly stated anything on or off the show regarding what taking in a grace that's not your own will do to your body, so it should be fine. Hope you guys enjoyed this chapter! :)