"A fast-paced, engaging fantasy novel that cat lovers will adore."—School Library Journal 

"Magical animals become a kooky, sweet metaphor for growing up."—Kirkus 

"Durst imbues her tale with humor, thoroughly embracing its unusual premise with a sense of wonder."—Publishers Weekly 

"Come for the horse-sized kitten, but stay for mystery, friendship, adventure and even more exceptional animals—Catalyst is a joyful read that's full of surprises!"—Emily Jenkins, New York Times bestselling co-author of the Upside-Down Magic series

Chapter 1

“NO KITTEN IS THAT SMALL,” the text from Harrison read. 

      Zoe texted back, “Smaller than my hand.” She crouched next to the tiny ball of fluff. Shivering, it had wedged itself between the trash can and the garage door. Zoe had spotted it when she’d dumped a bag of crumpled wrapping paper and used party plates into the can. 

      She cooed at the kitten, “It’s okay. Don’t be scared. You’ll be all right.” Checking around the garage, she searched for a mother cat or any other kittens, but didn’t see anything. She heard the chirp of crickets, cars on a distant highway, and the hum of her family’s voices through the open window of the brightly lit kitchen. But no meows. 

      Her phone binged with a one-word text: “Photoshop.” 

      “If Photoshop,” Zoe typed, “kitten would be riding a velociraptor.” 

      Bing. “Sweet.” Then: “Still Photoshop.” 

      “Come see.” 

      “Busy.” 

      She sent him an eye-roll emoji. He wasn’t busy. She knew for a fact that he was camping in his backyard, next to her own, and that he was most likely “busy” separating the raisins from the M&M’s in a bag of trail mix. Laying her hand flat, palm up, she waited as the kitten stuck out its little pink nose and sniffed her fingers. Zoe whispered, “Let me help you.” 

      The kitten crept forward into the light from the garage, and Zoe decided to think of it as a she, because the fuzz above her eyes looked like a cartoon cat’s eyelashes. She was trembling, which made her orange, black, and tan fur quiver all over. Her ears were flattened, and her tail was tucked between her hind legs. She looked so miserable and so hopeful at the same time that Zoe felt her heart melt. Poor little thing, she thought. “I can’t keep you,” Zoe warned. “My parents said no more animals in the house, not after the mix-up with the skunk.” 

      “Mew?” the kitten said. 

      “Long story,” Zoe said. “Tonight you’ll be my secret, and tomorrow I’ll help you find someone who can take care of you.” 

      She stayed still while the kitten sniffed her hand some more. Her nose and whiskers tickled, but Zoe didn’t laugh. Gingerly, the kitten placed one paw on Zoe’s palm. “You can trust me,” Zoe whispered. “Everything’s going to be okay. Promise.” 

      Cupping her other hand behind the kitten, Zoe scooted her fully onto her palm. She really is smaller than my hand, Zoe thought. She stood, cradling the kitten close. The kitten tensed and then relaxed as Zoe carried her inside. 

      Zoe heard the clink of glasses being loaded into the dishwasher in the kitchen as her parents and brother cleaned up from her birthday party. Her cousins, aunts, and uncles had all swarmed to their house for the usual hamburger, hot dog, and cake celebration and had left after Zoe opened her presents. Zoe was supposed to be in the kitchen, helping to clean. She tiptoed past and up the stairs to her bedroom. 

      Tucking the kitten against her with one hand, she used her other hand to drag a cardboard box from her closet, dump out her old rock collection, and line the box with a sweater. Lowering the kitten inside, Zoe told her, “Wait right here.” 

      “Mew?” 

      The kitten looked up with such wide eyes that Zoe didn’t want to leave her. She’d never had anything look at her with so much instant adoration. Certainly the box turtle—one of her last rescues prior to her parents saying no more—hadn’t cared. “One minute,” Zoe promised. 

      She hurried downstairs and into the kitchen. “Just thirsty!” she sang as she fetched the half-finished carton of milk from the refrigerator. She also plucked a bowl of mostly eaten popcorn off the counter. “And hungry!” 

      “Fine, but that’s it!” Mom called after her. “You’ve had enough snacks for one day.” 

      “Besides, you have to leave room for leftover cake!” Dad added. 

      Zoe’s older brother, Alex, cheered from the sink. “Second cake!” 

      It was a family tradition: second cake after the relatives had left. You ate a wedge with all the cousins, and then afterward, once cleanup was done, you could have whatever part of the leftover cake you wanted: just the frosting or just the innards or all the icing roses from on top . . . Zoe was not going to miss that. Those roses are mine, she thought. 

      “Don’t you think she’s getting a little old for second cake?” Mom said to Dad. 

      “I’m not too old for it,” Alex protested. 

      “Remember when we started second cake?” Dad said. “Alex was four, and it was the only way we could think of to keep him from scooping all the icing off the cake before the relatives finished singing ‘Happy Birthday.’” 

      I’m never outgrowing second cake, Zoe thought. That was a horrible thing to suggest. She was just getting taller and older, not transforming into some weird non-cake-loving person. “I’ll be right back,” she promised. “Don’t eat all the cake without me.” 

      She ran back up to her room, dumped the extra popcorn in the trash, and poured milk into the bowl. Kneeling, she nestled the bowl in the corner of the box. She hoped the kitten didn’t try to swim in it. 

      On wobbly legs, the kitten was prowling around the confines of the box. Reaching out a finger, Zoe stroked between her ears. “You don’t seem as scared as you were. That’s good. You don’t need to be scared with me.” 

      The kitten leaned against her finger as if she were so happy that Zoe was petting her. Most of the cats Zoe had met were standoffish, but not this kitten. She likes me! Zoe thought. 

      “I like you too,” Zoe whispered to her. 

      Climbing onto a mound of sweater, the kitten teetered, then toppled onto her side. Zoe laughed and helped her stand. Gazing up at Zoe, the kitten rubbed her cheek against Zoe’s fingers. She then got her paws underneath her and continued with her exploration. 

      Chin in her hands, Zoe watched the kitten reach the milk. She sniffed it and then looked back at Zoe. “Go on. You’ll love it,&rdqu...