Just do it before you lose your nerve.

I faced the door to Today, twirling Mr. Martel's—Adam's—coin in my hand, and letting the sharp edges of it press against my skin almost to the point of puncturing. It was seven in the morning. I could just leave, I told myself, pretend I hadn't even considered it.

Give him back his penny after seventh period and tell him never to speak to me again. Tell him I wouldn't play his games.

Or you could just do it.

The Today door wasn't like Yesterday, I assured myself for the millionth time. When you go into Yesterday even the smallest changes can ripple away, affecting everything and everybody. Yesterday is dangerous. Today is something else entirely. The Today door was just another version of your life.

I had come to think of Down World like the hairs on a human head. They look the same; they may even fall the same; they're probably about the same length; and when seen from a distance, they look like one body. But really, they are individual strands, twisting around each other, free-falling. And if you pluck one, the others remain.

Today is just another strand of hair. Look at it, touch it, smell it. But the other strands won't be affected either way.

You're overthinking this, Marina. Do it or don't.

Damn you, Adam. You knew I wouldn't be able to resist.

Before I could hesitate another moment, I slipped the coin into the slot of Today and held my breath. A jolting crash, like something heavy falling in another room, exploded for only a moment. And then, under the cracks of the door, the yellow light began to glow.

I took a deep breath, cleared my throat, and reached into my pocket. There I had stowed away a tattered train ticket stub, found in the crevices of my father's old briefcase, from when he used to take the commuter train to work.

I clenched it in my fingers now and opened the door.

As always, it started small. Yellow light, fading into colors. Technicolor reds, deep-sea blues. A breeze struck my face—no, not a breeze, a whoosh of air. From the train.

I was on the platform of the train station, and the train was pulling in, chugging and churning, coming to a stop.

And about half a dozen people were around me, suitcases in hand. This was the long-distance train. Westbound. The one I had taken with Brady two summers before. A suitcase brushed against my leg, metallic silver. Not my usual style. Had I borrowed it from someone?

"I'm so excited," Kieren spoke in my ear, leaning down from where he had been standing just behind me.

I gasped and tried to pass it off as a cough.

"Do you think Robbie will be surprised?"

I looked up at him, unsure, not wanting to give myself away. "Hmm?"

"When we show up at his birthday party? You think he'll be surprised?"

I caught up as quickly as I could, and nodded in response. "Yeah," was all I could think of to say.

"And he doesn't know we're coming, right?"

I shook my head, taking in the glint of excitement reflecting in Kieren's warm eyes. His eyelashes looked blond in the sunlight. He squinted to look down at me.

"Sorry," he laughed. "I'm nervous, I guess. It'll be the first time I've seen him since he said he forgave me. And I just... well..."

"It'll be great," I assured him. "It'll be perfect."

"You think so?" he asked, breathing through tight lips. He chuckled again, jittery and awkward. Beautiful and warm.

An old familiar sting behind my eyes crept up on me.

"What is it?" he smiled down at me.

"I'm just..." His crooked smile. His furrowed brow. "I'm just happy."

He put his arms around my waist and pulled me closer, tilting my chin up to meet him. "I'm happy too," he breathed.

I kissed him softly at first, shy suddenly. I hadn't actually kissed him that many times before...before I lost him. But he kissed me back with certainty, his lips firm, his strong nose nestling into the space beside mine.

"Okay, folks," said a middle-aged man in an official-looking railroad cap. "The overhead bins are full. If you've got luggage, hand it over and I'll stow it for you."

Kieren broke away, laughing a bit. He reached down and grabbed my suitcase. "I'll give him our bag. Meet you on the train, okay?"

"Okay," I whispered, watching him approach the porter. I wanted to drink in every moment of this, to see how he walked, how his shoulders had grown more broad, how his face had filled out. I watched him like a fleeting scene in a beautiful film, a perfectly composed image, there one second, gone the next.

I glanced up at the train, forgetting myself for a moment, ready to walk onto it and never come back.

At first, the image in the window seemed normal—just an old ticket taker walking past the rows of passengers. But when he was fully in the view of the window, I could see more clearly that he wasn't just a ticket taker, and he wasn't just a man.

The ancient conductor turned his head, slowly as though churning through molasses, in my direction. His skeletal face had not changed since I'd last seen it, barreling through space and time with Robbie and Piper on the DW train. The day that I had handed him Kieren's flattened penny; the day I had learned the power the coins possessed.

The conductor's hollow eyes bored through me now, his lipless smile twisting into a wicked grimace. He cocked his head slightly to the side, holding me in his vicious gaze. Then he raised up his index finger and shook it side to side like a pendulum: tsk, tsk, tsk. His wiry mouth mimicked the sound.

The message was clear: You don't belong here.

Panicking, terrified, I backed away. Further and further away. Until the colors began to melt.

I pushed away the reds and yellows and greens, the colors blending into formless mush, and the mush further melding into red brick.

I was back in the waiting room under the science lab, staring helplessly at the brick door to Today. My fists balled themselves into angry bombs and smashed away at that cruel, cold stone, over and over again, until my bloody hands couldn't take the sting of it anymore.

*

"My paper is on Joseph Stalin," intoned Angela Peirnot in her nasal voice. "So he was, like, the leader of Russia during World War II, right?"

We were sitting in another study group, just me, Angela, and Adrian Washington, while Adam circled the room like a hungry wolf, eavesdropping on everyone's conversations. I realized that I could only think of him as Adam now, not "Mr. Martel," ever since I found out he was the guy Brady had known when he was a freshman; the guy who had disappeared after going to see the Mystics.

"And he was supposed to be, like, a Communist, so he was supposed to be all, like 'Equality for everyone' and stuff, but really he was just a dictator?"

Angela had one of those voices that shot up at the end of the last word in every sentence so it came out as a question instead. I found myself resisting the urge to nod in agreement.

My knuckles ached from being scraped red on the brick door hours before, and my stomach felt sour from missing the beautiful version of life that had taunted me briefly in Today. How did DW do this to me every time? How did it suck me in when I knew better? Closing my eyes, I could still smell the sweet odor of changing leaves from the trees at the train station. I could feel the warm cotton of Kieren's sweatshirt, rubbing against my thin sweater.

"And so, like, they really hated the Germans, because the Germans, like... wait, I can't remember this part."

Adrian Washington, who had been grinning like a circus clown the whole time Angela talked, didn't seem to mind the interruption. He took the opportunity to tickle her kneecaps under the shared desk, which made her lose her place again in her loose-leaf stack of notes.

"Stop it," she giggled softly.

I buried my face in my hands, exhausted with this exercise and not really giving a crap if Angela Peirnot ever figured out who exactly Joseph Stalin was. It was ancient history now anyway.

"Mr. Martel?" she called out, probably not realizing how flirty her voice was when she said his name. Adrian Washington, however, definitely noticed. "Can you help me with this part? I'm super confused."

Adam walked over, and I kept my eyes glued to the desk. I could almost feel the weight of him straining to not look at me. "Yes?"

"So, like, I thought Russia was our enemy, right? Like there was a whole Cold War?"

"That's right."

"But, like, in this book I found a picture of Stalin and Roosevelt and the British guy—"

"Churchill."

"Yeah, him. Like, they were all hanging out?"

Unable to resist the urge any longer, I hazarded a glance up at Adam, only to find that he was staring right at me. He flinched immediately, regaining his composure and clearing his throat.

"And he was like this ruthless dictator..." Angela droned on. I took a deep breath, her voice getting under my skin. "I mean..." she flipped through some pages to find the right note. "Like, he starved his own people? And he sent all these people to Siberia?"

"What part don't you get?" Adam asked through tight lips, apparently as frustrated with Angela's obtuseness as I was.

"Why would we be, like, working with someone who we hated?"

"Germany invaded Russia. They hated Hitler as much as we did."

"Okay?" Angela asked, still not getting it.

Adam cleared his throat again, his eyes darting momentarily to the other students before returning to our table. "Have you ever heard the old Sanskrit saying, Miss Peirnot?"

Her perfectly defined eyebrows furrowed up at him, and her mouth turned into a pouty smile meant to make her lips look fuller. "What's that?"

Now Adam looked directly at me, the heat of his gaze forcing me to look up and meet his eyes. "The enemy of my enemy is my friend."

Refusing to break the staring contest first, I kept my head perfectly still until he broke away. Adam went to help another table and Angela sighed.

"Whatever," she whispered to Adrian, who shook his head, charmed by her apparently. He then began to tell us about his research into the Ugandan mass murderer Idi Amin.

When it was my turn to speak, I hurried through the choppy notes I had made on Genghis Khan, skipping many details as I knew my study partners weren't really listening anyway and the period was almost over.

The bell finally rang and I tried to leave before Adam could stop me, but he was waiting by the door. One look from him told me he needed me to wait behind, and I knew that if I left, he would only find me later. I stood frozen in the room while the clamoring students filed out around me, feeling like a child left behind at the circus.

When the room was empty, he closed the door.

"What do you want, Adam?"

"Have you decided?"

I let out a deep exhale—a breath I had been holding in all day. And though I wanted to scream at him, "No," or "I won't do it," or "It's not worth it," or any of the other denials that had been careening through my brain all day, all year for that matter, my mouth betrayed me by saying the only thing that I really wanted to believe, the decision that I had made the moment I saw Kieren's happy face smiling down at me at the train station.

I couldn't even look Adam in the eye to let him see my defeat.

"I'll do it."