Disclaimer: The Straw Hats belong to Oda-sensei. I am borrowing them without permission. I gain nothing but the joy of writing.

Author's Note: This story is rated 13+, mostly for language, violence and allusions to sensitive subject matter. It takes place after Enies Lobby/Water 7 recovery but before Thriller Bark. I tried my best to represent the different ways the characters address each other as accurately as possible, but I probably got a lot wrong. If you notice anything, please let me know.

Author's Note 2: Technically this is an AU if only because if this story happened, there would be some small changes to the very start of the Sabaody Archipelago arc. It's barely worth mentioning, but at least now you've been warned.

Diffraction
by Mako-clb

Chapter 1: Atmospheric Conditions

Nami scrutinized the map she had just finished of Enies Lobby. She had put this one off for as long as she could since it brought up difficult memories, but a map of the world would not be complete without it. Plus, Nami could claim to be the first and only non-Marine to ever map the island and its man-made tidal features, at least as far as she knew. Perhaps that would make up for the fact that it wasn't as perfect as she would like.

Nami was meticulous about her maps, and she had long ago developed a system to accurately and quickly map an island by taking a few surveying measurements and some visual observations. It was a skill she had learned through necessity as a child, but it served her well now. However, the battle at Enies Lobby had not afforded her a chance to do more than mentally catalogue a few major features. Still, it was one step closer to her goal.

Nami sealed up the ink bottle and moved to put her cartography supplies away when Usopp's booming voice made her jump.

"Nami! Storm! Big storm!"

Nami rolled her eyes. Of course Usopp would use the den den mushi speaker system on their new ship for a prank. Was he expecting her to rush out and get hit by one of his ketchup stars or something? Honestly, did Usopp want her to raise his debt?

Nami rolled her eyes and returned to storing her supplies. On a ship, it was never a good idea to leave things lying about unless you wanted them broken.

"Oi, Nami," Zoro said as he opened the door to the girls' room. "Didn't you hear Usopp? Big storm."

Nami frowned. It wasn't like Zoro to join in on one of Usopp's pranks. She quickly followed Zoro out the door only to see a huge sea of heavy dark clouds to the south. She ran down the stairs and across the deck towards the bow, where Luffy was still lounging in his favorite spot on the figurehead.

The clouds were still off in the distance. They were moving east, fast enough for her to notice but not fast enough for the storm to miss them if they stayed this course. Far ahead the waves were churning and crashing. Nami glanced to the west and noticed the sky was relatively clear. A change in course now and they could avoid the storm and prevent damage to the ship.

Nami looked up at the main sail. It was full, pulled taut and not whipping around. She closed her eyes for a moment and felt the wind at her back, then opened her eyes to see the storm clouds moving to her left. She felt the ship sway beneath her feet. The rocking was gentle. Thousand Sunny was larger than Going Merry, and Nami hadn't yet gotten familiar enough with her quirks to feel the waves through the ship, but the feeling didn't match what she was seeing in front of her.

"Sanji-kun, man the helm," Nami said, not bothering to turn, "but hold steady for now."

"Hey, don't let my ship get hit by lightning!" Franky bellowed as he pointed to the storm clouds where they could see flashes in the clouds. "That's not super."

"Don't you shout at Nami-san!" Sanji hollered even as he moved to the helm.

"Shut up! All of you! I'm trying to think."

Nami closed her eyes and concentrated on what she could feel instead of what she could see. The wind, the air pressure, the humidity, the gentle swaying of the ship all said calm seas and good weather.

She opened her eyes and saw large dark clouds and choppy water far ahead. A bolt of lightning flashed brightly, but she didn't hear any thunder.

"Nami, do something." Usopp's voice carried across the ship through the crow's nest speaker. "I don't want to die."

Nami clenched her fist and shook it in Usopp's direction. "I said, shut up!"

Everybody froze.

The first storm they encountered on the grand line had surprised Nami simply because she expected to see signs of a storm at the same time she felt them. Since then, she had learned to trust her senses and react to the slightest change in the weather. Right now, every fiber of Nami's being told her there was nothing in the air that indicated a storm before and nothing now. It was only when she looked south that her eyes said storm. She tilted her head, really looking, and she realized that even that wasn't right. The type of storm that would generate those clouds wouldn't be causing the water below it to move like that.

Nami closed her eyes again and really felt the air around her. She turned to the east then turned to the west, eyes still closed.

Nami opened her eyes.

"Sanji-kun, hold the course. Robin, Chopper, make sure everything is secure and tied down. Zoro, Luffy, get in place at the sails, but don't touch anything yet. Franky, be ready for a coup de burst on my mark only."

"Hey, Girlie, can't we just go around?"

"Don't question Nami-san!"

"Don't worry, Franky. Nami's the best." Luffy's voice carried across the entire ship. "Trust Nami."

Nami smiled, not that any of them could see.

The Thousand Sunny sailed straight into the storm. Except, it didn't. As the Straw Hats reached what appeared to be the edge of the downpour, the clouds just disappeared like some type of mirage.

-N-N-N-N-N-

To the west of the Thousand Sunny, a ship flying a jolly roger with a blue diamond over the skull's right eye drifted on the calm waters.

On the deck stood a tall, gaunt man with a salt-and-pepper beard and black hair that looked like it hadn't been combed in weeks. He grit his teeth as he watched his target. When it was clear the ship wasn't going to change course, he hurled his binoculars onto the deck and let his illusion fade.

"Captain?"

"They sailed right into the storm." The captain turned to his shorter, stouter first mate. "How the hell did they see through my illusion?"

"I don't know." The first-mate looked back out on the ship, catching the eye of their cook who tilted his head and gestured to the galley. "But we need supplies, so I suggest we head to Scaff."

"No." The captain turned around. "That ship must be heading to Horn Island. We can restock there. And I'm going to find out how they saw through our trap."

to be continued