Rat Boy watched his little sister Cecilia from the doorway of their burrow and counted the seconds she was out of reach. Their parents were gone. He was the only one who kept her safe. But Cecilia was five, quick, and never still. She darted between the clustered entryways of the burrow, chasing a beetle, her long tail whipping behind her. Rat Boy could not hold her hand every moment. He had errands. He had chores. And the moment he looked away, she wandered. "Stay close," he said. He said it a hundred times a day. Cecilia laughed and ran three steps toward the tall grass. Rat Boy's heart jumped. Past that grass was a slope, and past the slope, a road. He caught her tail gently and pulled her back. She didn't understand danger. That was his job. He needed to gather food before dark. But he could not carry supplies and chase her at once. Twice this week she had slipped away while his hands were full. Once he found her at the edge of the slope. He still felt sick thinking about it. Rat Boy sat on the burrow's step and thought hard. He needed a way to know when Cecilia strayed too far, even when his back was turned. Watching wasn't enough. He needed something that would tell him. He looked at her long tail. Then he looked at his own. An idea came. He found a length of thin, soft cord in the burrow. He tied one end loosely around his wrist. The other end he looped around Cecilia's tail, gentle enough that it never pulled or hurt. "What's this?" Cecilia asked, wiggling her tail. "A game," Rat Boy said. "You can play wherever you like. But if you go too far, I'll feel a little tug. Then I know to come look." He tested it. Cecilia ran to the grass. The cord went taut and tickled his wrist. He felt the pull before he even turned. It worked. But a fenced play yard stood a short walk away, with swings and a slide and a low wooden gate. That was too far for the cord to reach. If she played there while he ran errands, the cord would only stop her at the burrow. So Rat Boy walked her to the play yard first. He latched the gate. Inside, she was safe and enclosed, and he could feel the cord tug if she climbed toward the fence. "Play here," he said. "I'll gather food. The cord tells me if you reach the gate." Cecilia climbed onto a swing, happy. Rat Boy filled his arms with roots and berries, the cord light on his wrist. For the first time in weeks, he breathed easy. Then the cord jerked hard, twice, and did not go slack. Rat Boy dropped everything and ran. At the gate, the loose end of the cord lay in the dirt. Cecilia was gone.