Luna Lightbeam tightened her pink cape and pressed her face to the front window. A missing child was out there, trapped somewhere only her x-ray eyes could find. But Mom wouldn't listen. Mom was busy holding the new little sister. The baby had taken Luna's favorite spot on the couch. Luna's beach photo, the one in the brown wood frame, had been moved off the shelf to make room for baby bottles. Luna stared at it on the floor. Her green eyes burned hot and gold for a second, then dimmed. She stomped outside to the rainbow trampoline park dome at the edge of the yard. It was hers. No babies allowed. She bounced once, twice, then sat down hard in the foam pit. From here, no one could see her cry. Then she heard it — a small wail behind her. The baby had crawled out the door, dragging a stuffed unicorn with a pink mane. She clung to it and sobbed for Luna. Luna's jaw tightened. Slowly, she climbed down and held out her hand. "Okay," she whispered. "You can be my sidekick. But you have to keep my secrets."

The next morning, Mom buckled Luna and the baby into the car for a long drive to Georgia. Uncle Johnny had invited them down. Luna pressed her popcorn bowl against her chest, the one with the Supergirl screen still glowing behind it at home in her mind. She wanted her x-ray eyes to feel ready. They had to find the missing child soon. Uncle Johnny's place was nothing like the city. It was a dark log cabin with moss on the roof and crooked steps. Crickets screamed in the trees. A pink picnic basket sat on a checkered cloth in the yard, like someone had tried to make the spooky woods feel friendly. It didn't work. Luna marched behind the cabin and squeezed her eyes shut. She opened them at the wall. Nothing. No glow. No seeing through. She tried again, harder, until her head hurt. The gold didn't come. "It's broken," she whispered. Her hands shook. The missing child was so far away now. Too far. She kicked a pinecone and it bounced into the weeds. A fluffy golden puppy trotted around the corner, tongue out, tail whipping. She bumped Luna's knee and sat on her boot. Luna sniffed hard. The puppy licked her wrist. From the porch, Uncle Johnny called her to come sing into a sparkly pink microphone he'd set up by the steps. The baby clapped from her car seat. Luna picked up the puppy and held her tight. Her power was gone out here. But her sidekick was inside the car, and now this puppy was warm against her chest. She lifted her chin. "Okay," she said. "We'll find her from here. Somehow." The x-ray vision stayed dark. The mission stayed alive.