Posted originally on the Archive of Our Own at /works/16120463.

Rating: General Audiences

Archive Warning: No Archive Warnings Apply

Fandom: Hawaii Five-0 (2010), Percy Jackson and the Olympians & Related Fandoms - All Media Types

Relationship: Danny "Danno" Williams & Thalia Grace

Character: Danny "Danno" Williams, Thalia Grace, Steve McGarrett

Additional Tags: Crossover, Danny "Danno" Williams is a Demigod, Danny "Danno" Williams is the son of Zeus, That's why Danny is very iffy around Water, Danno and Thalia are siblings, Mention of Hawaiian Deities, Worried Steve McGarrett, Quests, Danny "Danno" Williams is a Protective Brother

Stats: Published: 2018-09-28 Words: 939

Title: Nā Manu Uila(Thunder Birds) by Merlin_Wolfgang_Trades_Hale

Summary: Thalia's in Hawaii on a job for Artemis and stops to visit her half-brother, Danny. They hang out and bond, but when Thalia's hunters have a lead to a very dangerous quest, Danny's not going to let her go alone. But he knows the dangers of two children of the Big Three being on the same quest...more so when that quest is on the seas and said children of the Big Three aren't children of Poseidon. Before he leaves, he gives Steve a quick call. Steve is of course worried. And he should be...Danny doesn't return as soon as he said he would.

Notes: The title name was just from a google translate. I don't know if it's correct so sorry if it's not.

"Does Artemis know you're here?" Danny asked as he placed the take-out on the counter.

"No. But we're only passing by. Thought I'd say hi, check in on how you're doing." Thalia said as she walked up to hug him.

Danny returned the hug and held on for a good moment. It wasn't often he got to see his half-sister. "That should be my job but you're quite nomadic these days."

"Well, you know how it is."

"I do. That I do..." Danny said. "Look, we can split the food but if you're still hungry we can go out and get something. How long are you in Hawaii?"

"Not long. We have our orders. We move out tomorrow night." Thalia told him.

"Well then. I'll call off tomorrow and we can hang out."

"You sure?" She asked as she reached for the carton of food.

"Course! What, my little sister comes through and I'm not gonna put everything aside and spend time with her?"

"You're a busy guy. A cop. A dad." She pointed out and they shared a look. Danny knew what that look was. Not many Greek demigods made it to adulthood, let alone to parenthood. So she had to ask. "What's that like? Do they have powers?"

"No. No uh...I uh...well, in Jersey things were different. I had a deal with a Hecate kid to help hide Gracie from monsters and gods and all of it...here, it's a different story. But I got it covered."

Thalia knew what he meant. Hawaii was full of its own rich history and had its own mythologies. "Have you had any run-ins?"

"Here and there," Danny replied with a casual shrug as he dug into his food. "Nothing I couldn't handle."

"And your team didn't question it?" Thalia asked with a raised eyebrow.

Danny let out a scoffing laugh, "Nah. Plus with a bit of the mist, any monster bite or scratch can be blamed on a perp or mission or hell, even my ex-wife."

Thalia laughed and they both ate in silence for a bit before she told him. "It's really good to see you. And that you're doing well."

Danny gave her a small smile. "It hasn't been easy. But...I manage."

"Son of Zeus in Hawaii...I can't really see it. I mean, it's pretty. Lots of nature and pretty cool animals but..." She gave him a knowing look.

"Yeah...I get why, but how?"

"Every month I pay homage to a lot of the local water deities around here. I respect them and they...they let me be. Hell, I even surf now."

That surprised Thalia a lot. "Seriously? You?"

"Yuck it up. Yes. And, I ain't half bad."

"You can't just leave. What about your kids?" Thalia asked as she stopped packing.

"We both heard your hunters. This lead you guys found, it's big. Bigger than what your hunters can handle."

"They're immortal. And very well trained."

"You're heading in uncharted waters. Literally. I've dealt with sea monsters and deities since I got here. I can get you through more than half of your route without anything to worry about." Danny promised her.

"And the rest? I'm guessing you wanna come along for that too?" She asked, already knowing the answer.

"I'm your brother. Of course I'm gonna go and cover your back. Look, I know this is still your mission. I know Artemis won't like this, like me going along, but I don't care. I'm used to sisters not liking me sticking my nose where it don't belong, but I do anyway cos I'm that annoying brother."

She knew better than to argue with him. Being a child of Zeus alone made Danny very stubborn, but Danny was even more so a special case. So she sighed, "Alright. Pack well. We leave in twenty."

"Gotcha," Danny said and went to grab his go-bag. It had most of what he needed for emergency trips, he only added an extra thing or two. He was at the 18 minute marker before he looked at his phone, then up to where Thalia was, then back to the phone. He went to his room and pulled up Steve's number. He answered on the fourth ring.

"Danny? What's wrong?"

"Uh...Steve, listen. I'm going to be away for a while, okay babe?"

"What? What do you mean away? Away where?"

"Look, Steve, I gotta go. Just know I'll be back. Take care of Gracie and Charlie for me while I'm gone, yeah?"

"Danny, what's going on? Danny, wait! I'll be right there, don't go anywhere!" Steve ordered.

"I love you, babe," Danny said as he hung up. He tossed the phone on his bed before picking up his bag and going to Thalia.

She had a disapproving look on her face. "Was that a good idea?"

"Probably not. But I know how these things go. I know the uh...statistics. There's two of us. Two wild, stubborn, hardheaded children of Zeus out on the sea...I just...it wasn't smart but it was needed."

Thalia didn't argue. She then used something Danny's never seen before to teleport them to where her hunters were lodging.

When Steve arrived not that long after there was no trace of where Danny was or where he was going. His go-bag was missing, so was his piece. But left behind were his badge and his phone. Steve did his best to keep calm as he called up, actually woke up, Jerry and the rest of 5-0 to get looking for Danny.

They wouldn't hear from him for another three hellish months.

End Notes:I wanna build up to Steve finding out about Danny being a demigod. Dunno if I'll ever reach THAT point buuuut...inspiration hit and so why not?