"What is it, Leo?" 

Percy poked Leo's newest masterpiece as everyone stood around it awkwardly. Leo had called them to Bunker 9 a minute ago regarding his latest invention. Everyone had thought it was to show them what it could do. It turns out, he called them there to figure out what it could do. "I don't know, Percy!" Leo said exasperatedly, throwing his hands up. "Well then, let's guess what it is and its function." Annabeth suggested. "How hard could that be? 

~some hours later~

Very hard, it seemed. They had been thinking for forever and still no idea what it was.

Piper ran her hand through her hair and said, "Well, looks like we're at a dead end guys. Have any more ideas?" 

"Maybe it's a robot," Jason suggested.

Percy sighed. They had been sitting in Bunker 9 for hours, thinking of what in Hades Leo's invention could possibly be. It was a weird-looking thing, with meters, levers, and a big blue button. Percy kinda wanted to press it, but he knew that wasn't really the safest thing to do. Who knows what it could do! It could wipe out camp, for one, or swallow them whole like Kronos. Yeah, Percy decided. I'll just play it safe and not touch it. Or at least that's what he thought he would do.

"Guys let's just call it a day" Annabeth sighed.

"Day? DAY!? We can't even call it a day, it's a night! Look outside!" Leo exclaimed, pointing out the door. The sun was almost down and Chiron would be calling for them by now. Hazel must've had the same train of thought as Percy, because she immediately scrambled to her feet and yelled, "WHAT ARE WE WAITING FOR!? LET'S GO!!"

No one had noticed she had accidentally flipped some of the levers on the machine as she got up. No one even saw the display change from the current year to somewhere in the 18th century.

"Yeah, Hazel's got a point there, we should go now." Frank said as he too stood up. "Okay then," Piper, Annabeth, Jason and Leo got to their feet as well, leaving Percy the only one still sitting down. Annabeth asked, "Percy, are you coming?" Percy replied, "Of course, Wise Girl. I just have to tie my shoelaces first. Don't wanna trip." He leaned on the machine for support. Don't touch the button. Whatever you do, do not press the button.

As Percy leaned on the machine to balance himself as he tied his shoelaces, he hit the blue button. Exactly what he didn't want to do. The thing started humming and whirring to life.

Ah, Styx.

Hazel jumped back startled as the button glowed. The machine's whirring intensified until finally it shot out beams of light towards the seven demigods. Demigods and contraption vanished into thin air.

What had just happened? 

The display on Leo's invention could explain it all. It read 1776, New York City. The demigods had gone back in time.