Hey guys! Thanks for reading the Sea of Time! This is the sequel to my previous Percy Jackson/Flash story Hurricane of Lightning. You are going to be really confused if you haven't read that one, so check it out if you haven't already. Let me get some housekeeping out of the way and we will get started:

1. This story contains spoilers for seasons 1-3 of the Flash. I will not be following the season 4 storyline, so you don't have to worry about any spoilers from that.

2. I don't own Percy Jackson or the Flash. Any plot points, characters, or objects referenced from the source material belongs to Rick Riordan, the CW, or DC comics. I only own my own plot.

3. As usual, I am going to try to keep author's notes short and sweet to avoid breaking up the story too much. In case you don't remember, the average time between updates is one week.

4. This story, I'm going to cycle in some different POV's (in addition to Barry and Percy). If you have any requests, feel free to let me know, but do so early on as I write rough drafts far in advance of publishing them.

5. These first two chapters are from Percy's earth. I wanted to explore how he was affected by the events of the last story and how Percy's oath impacts not only his friends, but someone whose fatal flaw is personal loyalty. But I'm not going to drag it out either, just add enough to show that it's there, then back off and get on with the story. Barry's struggles will come more from the events of the television show, from the end of seasons 2 and 3. I will make sure to touch on that in later chapters. Also, if you will allow me to step on my soapbox real quick, one of the qualms I have with the Heroes of Olympus (though don't get me wrong, I absolutely love that series) is that the effects of the character's experiences don't really seem to stick. I think this is probably the nature of writing for a middle school/high school audience, but it has always bothered me. I am positive that almost every single demigod has some form of PTSD or anxiety from what they have been through. This especially is irking when it comes to the main characters. I feel like it is really important to write characters who are inherently flawed (which Rick does really well), but also show that they are a bit chipped and cracked. They can't just walk off battles or time spent in Tartarus, because that just isn't the way life works. The most inspiring characters are the ones who pull themselves out of the dust, glue themselves back to together, and are stronger for it. That being said, I am not an expert on PTSD, so the way it manifests in these characters should not be generalized to all who suffer from PTSD. Okay, I'm done now. Thanks for indulging me.

6. This story is going to be rated T instead of the K+ rating Hurricane of Lightning has. Though the majority of the story (in my opinion) could be rated K+, I want to be safe rather than sorry when it comes to psychological trauma, canon-typical violence, and some very mild language. There will still be plenty of humor in this story though, so don't let the rating scare you off.

That's it for now. Thanks for reading and feel free to review, I love hearing what you all think of the story. Enjoy!

The sun was setting over the Long Island Sound, waves gently lapping the shoreline. Birds called back and forth, their songs dying off as the light disappeared. When darkness fell, the ocean felt deeper, something to be feared, like the legends of old. The unpredictable sea that Neptune reigned over, claiming legionnaires and praetors alike. But when the light hit the water again as the sun rose, the sea would be Poseidon's once more. Though ownership of most of the planet's surface never actually changed, its personalities were perfectly divided between the god's two aspects. The sea, never changing and yet always changing. The same could be said for the son of the sea.

Percy had taken to sitting by the water every day to watch the sun rise and fall above the Long Island Sound. A constant until the end of the world. The sun would always set in the west and rise again in the east. It grounded him, especially on his harder days. The years of war and conflict were starting to take a toll on the demigod. Time continued to flow past him, fluid and steady quantitatively, but when measured in moments it hastened then dragged. Annabeth had rolled her eyes when Percy said that, proceeding to explain the international time zones and daylight savings time. Science firmly said time was steady. Percy knew better. Because how could you trust time, when time itself can bend and shift, molding itself to one earth and not another?

Yes, he said one earth. No, he was not crazy or hallucinating. Although there were some days Camp Half Blood felt like an asylum, particularly when they set up the obstacle course. The theory of the multiverse (which was apparently a thing...not that anyone other than Annabeth and Barry's geek squad knew about it) was oh so very true. He had crossed over unintentionally, made some new friends, fought a dark speedster with self esteem issues, and came back once his aunt, the goddess of the hearth, had closed the breaches. And then he was banned on pain of death (and a very painful death as well) to never speak of his experiences. Which was easier said than done when your girlfriend was Annabeth Chase.

But he had returned, recovered from the brink of death, then by some miracle, finished out his senior year of high school with decent grades and gained admission to college in New Rome. The college was perfect: small with challenging coursework, lots of extracurricular opportunities, and 0% chance of his professor being a monster in disguise. He had just finished out his first year there, taking mostly general education courses that numbed his brain. Though they were much more interesting than mortal general education. Got to count your blessings when they escape from the tight grasp of the Olympians and hobble their way to you. College life was great, and being with Annabeth was even better. They were able to train together, study at the library, and just enjoy being on the same side of the country, without dealing with a prophecy or a war. Jason was there more often than not, and obviously Frank, Hazel, and Reyna were at Camp Jupiter full time. Nico popped by pretty often, and once Leo refurbished Festus, he and Calypso flew Piper up a few times for college visits. But now it was May, and the whole crew (minus Reyna, who was finishing out her last summer as praetor) were at Camp Half Blood. A whole year and a half since the multiverse expedition, about 2 years since the end of the Second Giant War. The Camp Jupiter crew would have to return to California, but they had a whole two weeks furlough to enjoy before they did. The group had of course asked more questions about his missing time, particularly when his panicked yelling during a nightmare about Greased Lighting himself woke Jason and Frank. But he stubbornly dodged their questions, telling half truths and internally cursing the gods of Olympus. They hadn't broached the topic again, and Percy hoped it would stay that way.

Percy sighed, splashing himself with the salty ocean water as the sun retreated back to the horizon. He stood, meandering back towards the camp along the coastline. They were having a campfire after dinner tonight, a celebration of the end of the school year and beginning of summer. Grinning at the thought of flaming marshmallows and Stoll brother pranks, he entered the mess hall. After grabbing a plate and making his sacrifices (with a little extra to Hestia, as he always did now), he made a beeline for the Poseidon table, where the rest his friends were waiting.

Though Chiron usually made all campers adhere to the "sit at the table of your godly parent" rule, he made an exception when the Camp Jupiter crew was here. It was surprisingly easy for their group to decide on the Poseidon table, as the only other option had the nasty habit of electrocuting anyone but Jason and Thalia. The Hades table might have worked, but even Nico didn't sit there anymore, ever since his powers mysteriously went awry during meal times. He had procured a doctor's note to sit at the Apollo table, and not even Chiron had decided it was worth arguing about. Tonight, the 7 plus Nico, Will, Calypso, and Thalia were gathered around Percy's table, laughing and throwing bits of food at each other. Life was good.

"Percy! Tell Leo that we absolutely do not need a flaming marshmallow catapult" Piper was attempting to restrain Leo from continuing to draw out his plans.

"Sorry, Pipes. I think that the whole camp would feel safer if we had some defense against the fearsome graham crackers". He glanced over Leo's shoulder, ignoring Piper's glare. "Why do you need Greek Fire?"

"How else am I going to light the catapult up?" Anticipating Percy's retort, Leo muttered, "Never mind. No, Leo, no greek fire for you. Why don't you just light it on fire yourself? In fact, let's get rid of all the Greek Fire and throw Leo at the monsters instead!"

"That sounds like a great idea, Leo. You would scare them right off". Calypso laughed and pecked him on the cheek when Leo looked offended, giving Percy a quick wave. He waved back, then settled down on the bench next to Annabeth.

"I really think that this would cut wait times at least in half, creating a much more pleasant death experience". Annabeth had her laptop out and was gesturing at some complex designs. "If Leo can make the microchip, I can program it to detect a person using facial recognition and biometric markers. The computer can then find them in the database and direct them to the appropriate line based on their historical life information".

"How is the computer program going to know their life?" Nico was frowning at the Annabeth's laptop while Will attempted to force-feed him a salad.

"That's the easy part. So much of the 21st century is online, the computer can flag mortals who are going to be sent to the Fields of Asphodel. That takes care of the majority of the mortal traffic. Those for Elysium or the Fields of Punishment will obviously need to go through the judgement process..." Annabeth continued detailing her plan, occasionally with input from Nico or Hazel, who was sitting on her other side. Percy turned his attention to his left, where Jason, Thalia, and Frank were having a heated argument.

"Come on, man. American football can be played all over the world, regardless of climate. Hockey is dependant on the weather". Jason's arms were flailing about as he tried to make his point, almost hitting his sister. She whacked him in the shoulder, then crossed her arms in disgust. Frank glared steadily at Jason, retorting, "You can play hockey anywhere in the world: it's called air conditioning".

"You guys are all missing the point. Why choose any of these so called sports with rules and regulations when you can watch mixed martial arts?" Thalia grinned smugly at them as if she had just proved their entire existence was a lie. "Nothing better than watching people beat each other up for sport".

"Isn't that what we do here?" Percy finally entered the conversation, ducking Jason's elbow and Thalia's glare. "If I want to watch someone get beat up, I just head down to the arena and watch Clarisse teach the new campers. No point in watching a tamer version of what we do on a daily basis".

"Then tell me, oh wise cousin, what is the best sport?" Thalia challenged.

"That's easy. Soccer. Most popular sport in the world by far, with 194 nations having a national team. Even North Korea has a soccer team. Fairly simple rules, lots of running, huge fan base...what?" Percy was baffled by the looks of shock he received from everyone at the table.

"You sound like Annabeth". Hazel blinked twice, as if trying to clear this hallucination that was an intelligent Percy Jackson.

"Don't get too impressed" Annabeth drawled, attention moving back to her computer. "He had to do a presentation on the evolution of an Olympic sport for our Ancient Greece in the Modern World course. Otherwise he would have said capture the flag".

Percy grinned, knocking his shoulder against Annabeth's. "She's not wrong, you know. Capture the flag is easily the most fun sport".

The conversations moved fluidly throughout dinner, participants switching off and new topics broached as smoothly as a baton in a relay race. Switching places at the table, eating off each others plates, using each other as footstools. Laughing, joking, catching up as only family does. The pavilion began to clear out as the younger campers headed out to the campfire, leaving their group of veterans to catch up. It couldn't get much better than this.

Of course, as if the universe was waiting for Percy to relax, Thalia turned to him. "So, Kelp Head, I heard that you gave camp a heart attack by disappearing again. Would have come to help but the Hunters have spent the last two years in Europe cleaning up Gaea's mess. Where did you end up this time?"

And just like that, the conversation died off. An awkward silence permeated the table, covert glances were exchanged between demigods and Percy tried not to hyperventilate. He cleared his throat, "Annabeth didn't tell you? Got kidnapped by a monster and was held for two weeks. It wanted my blood, thought it could get across the camp border that way. I lost a couple weeks of time, I think I must have hit my head or something. Next thing I knew Hestia was bringing me back to camp".

Thalia leaned her chair back on two legs, arms crossed once more. "Yeah, I heard that. Sounds like a load of crap to me". She held up a hand when Percy started to protest. "Give me some credit, Jackson. I've known you for six years now. You may not be able to lie well, but you are excellent at half truths. You did it when you bathed in the River Styx, when you were going to sneak onto our quest to rescue Annabeth and Artemis, to mortals after your disappearance. You are doing it now". Her voice softened incrementally as she leaned in closer to Percy. "Tell me the whole truth, Percy. We can only help if we know what's wrong".

The rest of the group looked uncomfortable but vaguely expectant. Hazel spoke first, seeming to grasp Thalia's train of thought.

"What happened to you, Percy? What was so bad that you can't even tell us?" Hazel gently inquired, swallowing nervously.

Percy laughed, a hollow thing without amusement. "I told you what happened. The details are unimportant".

Annabeth sighed, having gone through this conversation with Percy many times. Jason looked annoyed, almost disappointed. "Percy, you of all people know that the details are always important. On the most basic level, what if this monster figures out how to use your blood? What if this monster comes for one of us? Anything that can catch you off guard, much less hold you for a month, is dangerous to both camps".

The rest of the group held their breath, waiting for Percy's response. He looked at the one person who he thought could understand this. His cousin returned his gaze, nodding his head incrementally. Nico would have his back, no matter what the rest of the groups reactions were. Annabeth too, though he knew she wouldn't pass up an opportunity to learn more about Percy's time away.

"The monster isn't a problem anymore. Hestia took care of that". Percy calmly looked them all in the eyes, giving them at least something they hadn't heard before. "You don't have to be concerned. It's over. That's all I can say".

The group started to protest, their voices getting louder and louder as they tried to talk over each other, tried to talk sense into Percy, to get the whole story. It's like Thalia's inquiry set loose a whole year's worth of questions and demands for more information. Why didn't he trust them? This was a question of camp defense, and should be shared. Why do you have to be so stubborn, Jackson? Only Nico seemed to find the hidden meaning to Percy's words, mouthing "Styx" to Percy and seeming unsurprised by his affirmation. Will seemed to catch part of the interaction, and stopped pressuring Percy. The son of Apollo's patient was physically sound, and his boyfriend seemed to have reached an understanding with him. That was good enough for Will.

The voices grew louder, a clanging symphony that did little to calm Percy's nerves or growing headache. Like the sea changing from day to night, the son of Poseidon's temper grew short. When the noise grew too loud to bear, he finally snapped. Slamming his palms down on the table, he sent a small touch, a flick really, through the earth. The ground shuddered momentarily, the conversations stopping around him. His eyes grew more grey than green, their piercing glare landing on the entire group. "Enough. I've been patient with the questions, the side glances and the unbridled curiosity. That is all you are getting. I don't care if it's not enough, if it makes you think less of me. I. Can't. Tell. You".

He took a moment to reign in his temper, to pull back from the earth and remove the temptation. "I know that you were concerned. I know that this whole situation is annoyingly similar to the start of the Giant War. I know you care about me, and I care about you. You are my friends. I would want to know where you had been too. But these circumstances are different than our usual quests and prophecies. And the less you know, the better off you will be. So for your sake and mine, stop with the questions. Accept the answers I have given you because for now, that's all you're getting".

Percy stood up, rubbing his face and gathering his dishes. "I think I'll turn in early tonight. Enjoy the campfire. I'll see you all tomorrow".

And with that, Percy strode back to his cabin, letting his anger and frustration fade with each step. It wasn't their fault. He wasn't angry at them, not really. He was angry with the Olympians, that he had fought for the camps again and received orders to never speak of the multiverse for his troubles. Oh, thank you, hero of Olympus. Now shut your mouth and enjoy lying to your friends and family. Sighing, he realized he would need to apologize tomorrow morning.

He strode into his cabin, then promptly exited through the back. Percy could barely sleep on good nights, there was no way that he would be able to turn in now. So he went to the only place he could.

"I knew I would find you here". Annabeth's soft voice was barely audible over the crashing waves. "You can't seem to stay away these days".

"It's soothing. The water." Percy clarified, making room for Annabeth to sit next to him on the sand dune. "Not nearly as relaxing at night, but close enough". He shifted so that he was looking at her, regret filling his features. "I'm sorry for that, back there. I lost my temper".

"It was quite the show". Annabeth teased lightly, her head drifting down to his shoulder. They sat like that for a while, watching the waves roll in towards shore.

"You know that if I could tell you, I would?" Percy ventured hesitantly, hoping that this didn't count against his oath to never speak of the multiverse.

"Yeah, I got that. Finally caught it this time." She shifted slightly. "I trust you, Percy. And if you say that this monster isn't a problem anymore, I believe that. But you don't have the best track record of self preservation. And this experience, on top of everything else we have been through?" She paused for a moment, then barreled on ahead in typical Annabeth style. "I've heard about your nightmares. And some days you aren't all here. I know that's not exactly unusual after our time downstairs, but it's different. Because whatever is haunting you this time, we weren't together. How can I help you if I don't know what happened? I'm not frustrated with you, but with the big guys upstairs who apparently decided that we didn't need to know about your life anymore. That it was okay to use you and then throw you out into the world like nothing ever happened, just drop you off at the campfire half dead".

The sky rumbled ominously, but Annabeth didn't seem concerned. Neither was Percy, really. After a trip to Tartarus, the temperamental beings upstairs didn't seem nearly as intimidating. Percy and Annabeth had faced true fear.

"I'm not happy with them either. But this is our life, the good, ugly, and downright hideous. And there is nothing we can do but continue on the best we can". Percy answered, thinking of Barry Allen, the man who became the Flash despite his mother's murder. The universe wasn't fair to him either, but he made the best of it and moved on, tried not to look back. Percy was doing the same, one slow step at a time.

So together, the heroes of Olympus, two time veterans, and survivors of Tartarus watched the waves in a silent vigil against the darkness. It may not be evident now, but Percy knew that the sun always rose again.