It was a really nice day-the sun was out, and Hogwarts Castle had never looked more beautiful. With Voldemort gone, seventeen-year-old Harry Potter could finally relax. Students had been allowed to stay at Hogwarts over summer break due to the current circumstances (many people had lost their homes, their parents, or both). Harry sat by the lake, alone.

Suddenly, someone rose out of the water. He was about Harry's age, if he had to guess, maybe a year or two younger. Harry could tell that this stranger had also fought many villains and been on the run, like him.

"Who are you?" asked the boy.

Harry was surprised. He had just defeated the most evil wizard of all time-didn't he know who he was? "I'm Harry Potter, of course."

"Of course? Am I supposed to know you?" he replied. "My name is Percy-Percy Jackson. Don't you know who I am?"

Harry laughed. "So we're both famous in our own world. Where are you from?"

"Manhattan, New York," answered Percy. "USA. Where are you from and where are we now?"

"I'm from here," replied Harry. "We're near London, England."

"Oh," said Percy. "So-I'm assuming we're from different worlds. I mean, you'd know about me if we weren't. What did you do?"

"I defeated the greatest evil wizard of all time," said Harry. "That was about a month ago. And I had a lot of help. What did you do?"

"A wizard," muttered Percy. "Are you a son of Hecate?"

"Who?"

"The goddess of magic. I'm the son of Poseidon, Greek god of the sea. And I just defeated the first being ever to walk the Earth. Actually, she was the Earth. It's a long story. And I also had a lot of help," Percy told him.

"You're right about the different worlds," said Harry thoughtfully. "How did you get here?"

"Well, I was swimming in a lake back in New York," Percy explained, "And when I came up, I was here. By the way, I can breathe underwater."

"Oh," Harry said. "Well, that explains a lot. So, you said your father is..."

"The Greek god of the sea," Percy finished. "And my mom is a regular mortal."

"A Muggle," said Harry. "You'd know if she weren't. My parents were wizards, and so am I, and so is everybody else here."

"Muggle?" asked Percy.

"That's anyone who isn't a wizard or witch," explained Harry.

They were silent for a little while.

"So, uh, what can you do?" asked Percy.

With a wave of his wand, Harry made an ant grow, then shrink, then catch on fire, then turn into a teacup.

"Cool," said Percy. Then, turning to the lake, he caused small waves, which grew a little larger. "I can summon hurricanes, too," he said. "But it takes a lot of my strength."

Suddenly, a huge shadow blocked the sun. Screams could be heard from the castle. A voice boomed:

"I AM THE DARK AND THE EVIL THAT LURKS WITHIN EVERYTHING. FOR TRILLIONS OF YEARS I HAVE SLEPT. I AM OLDER THAN TIME ITSELF. AND I HAVE BEEN FORGOTTEN. BUT I WILL BE FORGOTTEN NO LONGER! YOU HAVE SEVEN DAYS BEFORE I FULLY WAKE. PREPARE YOURSELVES. IF YOU JOIN ME, YOU WILL BE SPARED. EVERY BEING WHO DIES IS A WASTE. JOIN ME, AND YOU CAN RULE WITH ME! YOU HAVE BEEN WARNED! MWAHAHAHAHA. HAHAHAHAHAHA!"

Harry and Percy sighed in unison.

Time to save the world...again!