At the bottom of the stairs, we found ourselves in a circular chamber with three separate doors.

Great. It hadn’t gone so well the last time we’d had to pick a path. Tree-shaped lanterns hung from the walls between the doors. Inside of each sat light spirits, looking bored. They were basically identical to fire spirits, except they shone white. One of them had joined their friend in a neighboring lantern to play Pictionary in the dusty glass.

The first door was black and engraved with roots that looked like snakes all twisted together. It made my skin crawl.

The second door had flowers carved along the bottom of it, with blossoms of purple and blue. The brown frame had been painted to look like it was covered in green moss, and it was rendered in such detail that I could imagine the spongy feel against my fingers.

The third door displayed tree branches in the full bloom of summer, pale brown with rough strokes of green representing leaves, set against a sky-blue background. It looked cheerful and bright, even in the gloomy chamber.

“Which one should we take?” Zhong asked.

I wanted to say that the last door looked like a good choice. But my brother’s life was on the line. We couldn’t afford to get it wrong.

I joined her in front of the first door. “Are those words up there?”

Scrawled into the wall above the door were the letters CAG NTOO. The second door was labeled CEV NTOO. The third was CEG NTOO.

“What do they mean?” I asked, a little ashamed that I couldn’t read the Hmong words.

“Roots, trunk, branches.” Zhong pointed to each as she read them.

“That does make sense,” I said, indicating each door’s design. It was nice of the tree to supply visual aids.

“I like the sound of branches,” Miv said. “Maybe that one will lead aboveground.”

“Who put the ax in here, anyway?” I asked. “Was it Shee Yee?”

Miv answered, “Supposedly, it was his mother. After he died, she placed it here so that it would remain with his soul. Neither of them was ever meant to leave the tree.”

Zhong crossed her arms, drumming her fingers against her skin. “So then maybe she put it in the branches, because if he was never supposed to be reincarnated, she would want him to eventually move on to the realm of the ancestors.”

“Like I said, branches,” Miv said, throwing up his paws.

It did make sense. But something Yeng had said bothered me.

Can you face your own soul, Pahua Moua?

My soul, not Shee Yee’s.

And why would that be difficult? My life was already pretty pathetic. My best friend was an invisible cat, I didn’t fit in at school, my dad was gone, I hadn’t spoken more than a few sentences to my mom for weeks because she was barely home, and my social circle consisted of exactly one other person—Matt.

But something tickled the back of my mind. Before my dad left, my parents used to talk about how they wanted to spend more time teaching me and Matt the history of the Hmong, and our traditions and customs. They’d wanted us to know our cultural roots. My dad said that, even as our branches grew, our roots did, too, soaking up all our experiences. Maybe…

“It’s in the roots,” I said.

Miv and Zhong both looked at me suspiciously.

“How do you know?” Zhong asked, eyes narrowed.

“I don’t. I just have a feeling.”

“That’s reassuring,” Miv said. “Is this like the time you just had a feeling you should eat that two-week-old cookie? You had a very different feeling after—”

My face went hot. “Not like that! This time I’m sure it’s the right choice.”

Zhong didn’t look entirely convinced, but she said, “Now that you mention it, it sounds like what I learned in school about the cycle of reincarnation. The roots are the part of our soul that will always remain us regardless of how many times the plant has withered and regrown. The trunk is our current form, and the branches represent a higher state we can achieve when our soul is finally allowed into the realm of our ancestors. If you’re certain the ax is in the roots, I guess we’ll have to trust your feeling.”

I appreciated her saying that. I gave one last longing look at the brightly painted branches door. Then I grabbed the roots doorknob and twisted. It swung open easily to reveal a tunnel.

“Why did it have to be roots?” I sounded pitiful even to my own ears. But if this was the path I had to take to save my brother, then I had to get moving.

The floor was firmly packed dirt. Thick, fibrous roots pushed through the walls. More tree-shaped lanterns hung from the ceiling, so it wasn’t as gloomy as it could have been. The light spirits stared as we passed, their large eyes narrowed warily. They probably didn’t get many visitors here, much less living mortals. The tunnel curved, so there was no telling how long it was. There were a lot of doors, though, most of them wide open. It felt awkward to be trooping through what was most likely Yeng’s living space.

“Is the arborist a nature or guardian spiritfolk?” I asked Zhong.

“Both, probably.”

I peered through the first door into what looked like a completely normal room. A stuffed chair sat beside a fake fireplace (we were still inside a tree, after all—well, underneath it, anyway—and everything was super flammable) and an end table stacked with books. I tilted my head to read the spines. Home Remedies for Frog Spirit Warts. Yoga for Snakes: No Limbs, No Problem. A History of Fashion for the Perpetually Broke. Twilight.

The next room’s walls were completely covered with mirrors. A dozen mats were spread out over the floor. I guessed we’d found Yeng’s yoga room. A calendar with a bright X on it marked her next session.

The rooms got increasingly weird after that. One was completely dedicated to rainbow-themed stationery. It was like a unicorn had exploded in there. Another was filled with clothing racks organized by profession and time period, like DASHING PIRATE, 12TH-CENTURY CHINA or IMPERIAL NAIL CLIPPER, 4TH-CENTURY ITALY.

There was also a truly impressive shoe closet, where I traded my sandals for a pair of sturdy boots. I figured Yeng wouldn’t notice, and we were almost the same size. Zhong tilted her nose in the air and pretended not to see.

At last we reached the end of the corridor, which opened into the biggest room yet. It was a library, filled wall-to-wall with books. Instead of dirt, the floor was checkered tile that had faded and cracked.

“This isn’t so bad,” I said, even though I wasn’t much of a reader. It also smelled a little musty, like it hadn’t been dusted in a couple of centuries.

Zhong, though, looked like she had walked into the Sky Father’s heavenly garden. If she’d been a cartoon, there would have been hearts in her eyes.

“This is amazing!” She spread her arms wide, like she wanted to hug the shelves.

“It’s cool, I guess,” I said. A library was a lot less menacing than what I expected, given Yeng’s warnings.

Zhong was too happy to even try to look annoyed with me. She rubbed her fingers along the dusty spines to try to read the titles.

“There’s the exit,” I said, pointing to the other end of the library. A narrow wooden door stood open, leading who knew where, but it looked like the fastest way through.

Something hard hit my shoulder blade.

“Ow!” I spun around. A book lay on the ground behind me. “Zhong! Why are you—”

“What?” she asked. She was standing right next to me. It couldn’t have been her.

Puzzled, I said, “Someone threw a book at me.”

We squinted into the dark corners of the library.

“I don’t see anyone,” Miv said uneasily.

“Who’s there?” I demanded, and then gasped as a book flew off the shelf and came hurtling at my face.

I ducked as the book shouted, “In the mortal realm, a full moon occurs every twenty-nine-point-five days!”

“What?!” My eyes widened as the first book lifted off the ground by itself.

“Some oranges stay green even when ripe!” it declared before flinging itself at me.

“Aah!” I dodged, falling onto my side. My elbows skidded painfully across the tiles. Miv jumped onto my face, smacking me with his paw to make me get up.

The second my feet were beneath me again, I ran. More books left their places on the shelves to fly at us. One hit my leg. Another my shoulder and arm. A third jabbed me in the cheek, narrowly missing my eye, and they all shouted random facts.

“One bolt of lightning can toast one hundred thousand pieces of bread!”

“Only two percent of the global population has green eyes!”

“Sarcasm makes you more creative!”

Zhong shrieked as a book smacked into her nose. “We’re being pelted with knowledge!”

“Run faster!” Miv said, hiding beneath my hair.

We sprinted across the floor, arms raised to protect our heads.

The corner of a book stabbed the back of my neck. “Because of a genetic defect, cats can’t taste sweet things!”

“Really?” I asked Miv, even as I slapped the book away.

“Not now!” he yowled back.

A particularly thick book slammed into the back of my leg. I fell with an oomph. My palms slapped the floor, stinging.

“The T. rex probably didn’t roar. Scientists think it hissed or rattled like a rattlesnake!” the book said.

“Stop ruining Jurassic Park!” I shouted at it.

Zhong reached down with one hand to haul me up. “Keep going.”

I struggled back to my feet, limping. The door was just a few paces away.

A book behind me shouted, “The god of thunder, destruction, and wrath was defeated by Shee Yee with his celestial ax!”

I almost tripped again when I spun back around. A book tried to whack me in the temple with its cover. I swatted at it, but that didn’t help much. Books surrounded me, each shouting to be heard over the others. Their hard corners and sharp edges dug into my skin. I really didn’t want to die by a thousand paper cuts.

Then, suddenly, they all flew a few feet away. I groaned in relief and peeked out from between my arms. Zhong stood next to me, holding a stack of flaming paper—some of her talismans—that she’d lit with the lighter in her other hand. The books, apparently understanding the danger, had backed off.

“Come on, let’s go,” she said to me, sounding breathless. A bruise was forming above her left eyebrow.

But I had to find out something first. “Which one of you mentioned Xov and Shee Yee?”

All the books began talking again at the same time.

“A single elephant tooth can weigh up to nine pounds.”

“Queen Elizabeth II refused to sit on the Iron Throne because it was foreign.”

“Shee Yee, the grandson of the Sky Father, was especially fond of goat cheese.”

There! I snatched the thin blue book. It fought me, trying to snap my fingers between its covers, but I clutched it to my chest. The other books closed in again, but Zhong dropped the last of the paper talismans, now ashes, and waved her lighter in the air threateningly. Then we darted out the exit door and slammed it shut behind us.