Nellie agrees. “We need to stop him before he goes in. Demand answers. He can’t pretend he doesn’t know what we’re talking about when he has just led us to his evil headquarters. No one lives in a secret mountain unless they’re up to something!”

Eli bends down. His gloved hands move swiftly, forming a perfect snowball.  With one hand, he hurls the snowball at the custodian. It slams into his back, and the custodian almost topples over.

“Who’s there?” he calls. In the wind, the snow whirls around the pathway like a blizzard. “Hello?”

Nellie scrambles forward, Eli beside her with Squizzle still perched on his shoulder. “It’s time for an explanation.” She folds her arms. “We know what you’ve been up to.”

The custodian looks nervous. “Listen,” he says. “It’s not a big deal. I’m just doing a little extra work.”

“A little extra work that’s terrorizing the welcome house!” Eli says hotly. Squizzle shrieks in agreement. “What’s Mr. Teichman going to say when he finds out?”

The custodian’s eyes narrow. “Look, kids, it’s not your business. It’s all under control.”

“It’s clearly not,” Nellie points out. “You’re trying to destroy all of their hard work.”

“What?” Now the custodian looks puzzled. “How am I doing that?”

Eli holds up the compass. “You tell us! The windows? The heat? The locks?”

“I didn’t do any of that!”

Nellie glares at him. “You just admitted you were up to something!”

The custodian frowns. “Right. I’m supposed to be working at the welcome house full time. But I took a second job here. If Mr. Teichman finds out, he’ll be very unhappy. But Dr. Zapf pays me well for a couple extra hours a day.” He gestures at the entrance.

“Dr. Zapf?” Nellie repeats. She ducks down to peer inside, and Squizzle jumps off of Eli to inspect the entrance. The doorway opens to a corridor downward into the mountain. After a few steps in, the ceiling is high enough that Nellie can stand up straight. Eli stays close behind her, the custodian trailing at the back.

“If the custodian isn’t the one reversing everything, then who is?” Eli murmurs.

Nellie scowls at the icy walls around her. “My bet is on Dr. Zapf.”

Walking through a mountain, surrounded by ice on all sides, is the worst thing that Nellie can imagine. But to her surprise, the deeper they go, the warmer it gets. Somehow, the ice is insulating the mountain from the cold and wind.

In the center of the mountain, the hallway widens into a huge room. A laboratory. There are test tubes and vials on shelves attached to the walls and a huge table in the center. All kinds of colorful chemical solutions sit on the table, some still smoking, and there’s a metal structure on one side that is shaped like two pipes twisting around each other. There are tools and books stacked on a counter  in front of the shelves, enough that Eli would probably be happy here for weeks, and right at the center of the room stands a tiny woman with long white hair and huge goggles. “Oh, hello, Anton!” she says happily. “And you’ve brought some of your friends!” She bends down to hold a hand out to Squizzle. Squizzle draws back, looking alarmed. Nellie is pretty sure that this must be Dr. Zapf.

Dr. Zapf holds up a strange-looking item, a metal ball coated in ice with curved tubes on either side of it. “This will change everything,” she says, flipping the item over. “I’ll be able to write this into major scientific journals. Those researchers who laughed at me will never doubt me again.” She turns in a circle and does a little dance, then blinks at Nellie and Eli as though she’s only just remembered they’re here. “Oh, my. You’re very small for a cleaning crew.”

“We’re kids,” Nellie says. She isn’t sure Dr. Zapf is listening to her. Already, Dr. Zapf has returned to the table, mixing two smoking chemicals and adding them to a vial on a burner. When she turns on the burner, the solution bubbles. Dr. Zapf lets out a noise of delight, then pours the vial into the curved tubes of the strange item.

“Brilliant!” she says. “Oh, I am brilliant! This’ll be the talk of the town! They’ll write books about me! Every scientist in the world will know my name!”

“She does this a lot,” the custodian whispers to them. “Then something goes wrong, and it explodes. I just clean up the mess.”

But Eli looks interested. “What did you make?” he asks, leaning forward to see it.

“I’m glad you asked, young man!” Dr. Zapf cries out. “Why, it’s a polarity reverser. When activated, it creates a magnetic blast that affects the Earth itself.” She beams at them. “I call it the Pole-Reverse.”

“The Pole-Reverse,” Eli echoes. Nellie exchanges a glance with him. “You mean, like the North Pole?”

“I mean, little lady,” Dr. Zapf says, and she lifts her Pole-Reverse in the air, fingers curled around the loops. The chemicals inside it bubble and shimmer, and the ice seems to grow stronger as they move through it, over the metal ball and to the other tube. “That when I use my new invention, you might as well call this place the South Pole!”

She flips the Pole-Reverse over, then checks a large compass on the table. Eli takes his own compass out, and Nellie peers at it. The arrow, which had been inching toward south again, whirls around to point north.

At the same time, every vial on the table flips over, spilling chemicals everywhere. A clock on the wall switches from a.m. to p.m. And a sheet of ice appears across the doorway of the room, blocking them off from the hallway to outside.

“How fascinating,” Dr. Zapf says, tilting her head. “We appear to be trapped.”

(Originally featured in Treeo, Issue 1002)