What began as a just fine day was fast sinking into sludge.

Addy had been eager to help Uncle Vim carry boxes of Flynn Goster back issues to the big comic convention. Total fun to be at ComicFest—plus, even a dribble of cash was always welcome. And there was no adult she’d rather hang out with than Viminy Crowe.

“If you want to bring a friend …?” he’d said.

“Nuh-uh.” Even to Vim, Addy wouldn’t admit that she didn’t exactly have any friends.

Her mother—who had to work, as usual—told Addy she shouldn’t take Catnip along. But Addy, naturally, had smuggled him out of the house inside her shoulder bag, keeping nose and whiskers hidden during the whole carton-hauling interlude. Once they got to the convention center, disaster struck. First, she had to watch her uncle lose what little cool he had (and, really, cool he wasn’t) when the giant train display for the booth began to malfunction. The way it was supposed to go, you “climbed aboard” by stepping up onto a little platform behind a windshield and—whoopee!—turning an oversized steering wheel. A glowing orange spotlight was supposed to beam out from the front of the engine. Pulling on a silk cord sounded an old-fashioned train whistle. Only this morning, the light didn’t work, and the noise was more like a cow mooing than anything mysterious and steampunk-y to go with the comic.

Addy and Uncle Vim had dragged the display off the exhibition floor to the service area to await the repair team. Back at the booth, Vim raked his hair with his fingers, trying to figure out how to decorate without the cutout gold rush train. And that’s when he realized that the ten thousand copies of the new Summer Special had not been delivered.

“Tomorrow?” he shouted into his cell phone. “What do you mean, tomorrow? I could be dead tomorrow! My own blood is in those pages! Blood and sweat—even a few tears. Today is the opening day of ComicFest. TO. DAY! Now! This minute! Before the toast pops up, you get it? Hordes of rabid fans are waiting to buy this issue! Tomorrow is not acceptable!”

He prowled back and forth in the aisle like a panther in a crummy cage, ranting into the phone while the hordes watched.

Kind of loving the show, Addy thought. Except it wasn’t a show.

Uncle Vim urgently needed this comic book to be a success. The first issue, Flynn Goster and the Curse of the Diavik Diamonds, had done okay. The critics hadn’t really paid attention, but readers started to pass the word around that Viminy Crowe was an awesome new comic artist. The second issue, Flynn Goster and the Emeralds of Green Gables, sold like crazy. That’s when Vim got a call from FunnyBones Comics offering to invest in Issue #3. They’d pay all the printing and distribution costs—in other words, they’d take all the risk—which was great, because Uncle Vim was at the very end of his money options. All he had to do was create the most brilliant comic book ever and guarantee that it would sell like buttered popcorn at the movies.

Those missing cartons held his future, even his life, as far as Vim was concerned. His older sister—Addy’s mom—had been supporting him all this time, contributing money she saved from working two jobs. She knew her brother was a genius artist, but this was pretty much his last chance to prove it to the world. If the FunnyBones guys stayed excited and their investment paid off, maybe they would publish a whole series! But if the comic flopped … Addy’s stomach did a small flop of its own. If it flopped, Uncle Vim was planning to move back to Saskatchewan and his former job at the Petalskin Soap Company, living a million miles away, letting his dreams of being an artist get sucked down the drain like old bath bubbles.

Addy’s phone made its ding-dong doorbell sound, telling her there was a text from the person who slept on the living room couch.

all good? wrote Vim.

yep she sent back.

i have a break in an hour. u good til then?

yep she wrote.

Then, just when Addy finally got to a nice quiet table (she was pretty sure Catnip was expiring from lack of food and air), this dweeby kid sat down—with onion rings tormenting her nostrils!—thinking he was Addy’s best friend, yakking away like an old lady you might get stuck next to on a train. He had the kind of round, freckly face that you’d see on a commercial for, say, phony homemade apple pie. He was round all over, actually, and his pants had those bulgy pockets, making him look even wider.

As long as he was sitting there, Addy didn’t want to feed Catnip. You never knew who would object to the sight of a rat chomping lettuce in a public food court. She pretended to be enraptured by the sample copy of Issue #3, the Summer Special, a story she knew as well as her own toothbrush, since she had basically helped her uncle to write it. Well, maybe not actually write it, but she’d given him a whole lot of ideas. And no one could deny that Nelly Day, the young heroine and sneak thief, had Addy’s eyes, her nose, her one dimple and her messy dark hair.

When Uncle Vim had clogged up the plot with too many complications, it was Addy who reminded him to “Keep it simple! It’s all about the gold.” He’d been so grateful for her input that he brought home an add-on rodent terrace for Catnip’s ever-growing estate on the kitchen windowsill.

Plus, this kid? Wylder Wallace? (What mother names her kid Wylder Wallace unless she expects him to be goofy?) Addy didn’t want to be mean, but he was having a major fan-attack about meeting Superman in the lunch line. While she had done her best to avoid the caped superdrip. True, Bob Fink did look the part. But holy cannoli, he might be the most boring dude ever! He’d showed up at Uncle Vim’s barbecue last summer, on the back terrace of Addy’s apartment building, one of dozens of people Vim had met through work. Half of them were actors who impersonated comic book heroes. (It was one thing, in Addy’s opinion, to create a comic book. But to spend your life pretending to be in one? Come on!)

That night, Bob Fink got “overly fond of the beer,” as Addy’s mother put it, and started to sing, revealing the reason he was usually hired to stand around in tights and a cape with his mouth shut, instead of on a stage next to a microphone.

And now, Wylder Wallace had spilled salad dressing across the table, so Addy had to scram out of there with icky sludge all over her only pair of jeans. And when she got to the washroom, there was one of those annoying yellow signs dangling on the door: CLOSED FOR CLEANING. SORRY FOR THE INCONVENIENCE. PLEASE USE FACILITY ON LEVEL C.

Level C? Level C was all the way across the convention hall and up the escalator. The slimy orange gunk would probably have burned a hole through the denim by then.

Addy slipped a hand into her bag to stroke Catnip’s head while she thought for a second. There was a staff-only restroom behind the food court, near where they’d hauled the broken train display that morning with Uncle Vim looking miserable. Addy had felt a lurch of pity for him.

“No comics,” he’d said. “And the display is broken. I want it fixed by the time I take it home.”

“I’m sure my mom will love that.” Addy rolled her eyes. “Not.”

A floor-to-ceiling curtain hid the scruffy “backstage” of the convention center and the staff washroom from the general public. Addy slipped through a break in the curtain and bumped smack into the broken train display, right where they’d left it. A flash of light bounced off the ladies’ room door but then went dark at once. Addy reached into the engineer’s cabin to toot the horn. Moooo.

Never mind. Poor Uncle Vim.

The door with WOMEN/FEMMES in fat black letters was luckily not locked. But the lights were out. She flicked the switch—on the wall outside the door—and the lights blinked dramatically with an amber glow. There was a noise, a sort of clicking and huffing at the same time. Seriously creepy. Addy would make this quick.

She snatched a towel from the stack beside the sink. Nice that it wasn’t paper—wet cotton wouldn’t shred all over her jeans. The lights kept flickering as Addy dampened the towel and scrubbed at the salad dressing. She looked around to see if there was one of those air-blowy things to help dry the big spot on her pants. No dryer in sight, so Addy waved her hand over the spot and blew on it, as if that would do anything.

The floor began to shake. Addy clapped a hand over the top of her bag to protect Catnip if she lost her balance. Was it an earthquake? The door sprang open and a girl came in, slamming it quickly behind her and then pressing her ear against it, listening. Even in the dim light, Addy could see that she was an actor in costume—a familiar character but not a superhero. She was wearing clunky laced-up boots, striped leggings and a cool utility vest with loads of pockets.

“Um, hello?”

“Aahhh!” The girl jumped and swung around, raising her fists as if ready to punch Addy in the nose.

“Whoa!” said Addy. “Didn’t mean to scare you.”

The ground shook again, and the lights dipped to nearly black.

The girl whispered from the shadows, “Keep your grimy hands off me, you mud-licking squit!”

“What?” Addy couldn’t believe she was being snarled at. “I have a right to be here. I’m with the Goster booth. Number 418.”

“I’ve watched every person on board,” said the girl. “I only slipped in here to avoid the creeping brat who trails around after the suspicious professor. I’ve not seen you before, so I’m thinking you’re fishy too. You’re no friend of Aunt Isadora’s. You’re not a Rider. I’ve memorized everyone, so I know you haven’t got a proper seat.”

Holy cannoli! Addy should have recognized the character at once. Her words got all mixed up spilling out: “But-Isa-baba-Unca-Vim-fa-Rider-da-gold-rush … ON BOARD WHAT?”

She paused to breathe and got a clear look at the girl’s face. “Who are you?” she said.

They stared at each other.

“Who are you?” said the girl.

As if both their necks were on the same hinge, the girls turned to gaze into the scratched-up mirror above the sink. Two pairs of gray eyes stared back in surprise, before snapping around to face each other.

“I’m impressed,” said Addy. “How did they find someone who looks even more like Nelly Day than I do?”

“I am Nelly Day,” said the girl.

“You don’t have to worry about keeping in character. I’m not some crazy fan who needs to believe that you’re real.”

The girl narrowed her eyes. “I am Nelly Day,” she said again. “Who are you?”

“It’s okay,” said Addy. “We’re in a washroom at the Toronto Convention Centre. You’re not destroying some childish fantasy that Santa Claus or Superman or Flynn Goster actually exists.”

The ground continued to rumble under their feet. The flickering light added to an unpleasant feeling of motion.

“Are we having an earthquake?” said Addy. “I’ve never heard of Toronto getting earthquakes. And what do you mean, on board?”

The actor squinched her eyes at Addy. “Are you loco?” she said. “How did you get here if you don’t know? What kind of a sneaking rat are you?”

Addy slipped a hand into her bag to check on Catnip. Nothing wrong with rats, in her opinion. Rats were supreme beings, with a family heritage going back beyond ancient Egypt, while Nelly Day had been invented by Addy’s uncle six months ago.

Things were getting a little too weird. Addy had no intention of standing around listening to insults from an actor! She nudged the other girl aside and opened the door.

She slammed it shut again—BANG!—her stomach turning upside down.

Instead of the empty, beige-curtained corridor of the convention center staff area, Addy had seen a row of grimy windows. And beyond the mud-spattered glass was an unfamiliar wilderness, rattling past the way it does when a person is sitting on a—

It was impossible.

Addy was on a train.