Holly Graye wanted to be the youngest master cartographer the scholars' guild had ever admitted, and the guild had just told her no. The judge slid her half-finished map back across the desk. It stopped short of the river's far bank, where the ink faded into blank paper. "We cannot rank a map that ends in the middle of the water," the judge said. "Finish the crossing, girl. Then we'll talk." Holly rolled the map with shaking hands. The river was the problem. Her old surveying chain sagged and slipped. Her sighting rod was warped from three winters of rain. Master-grade work needed clean angles, and her gear gave her mud. She climbed down to the riverbank at dawn to try anyway. Her wolf padded beside her, its white coat catching the light like frost. It stopped at the water's edge and would not follow. It lowered its head and growled at the shallows. Holly waded in with her chain. The current pushed against her knees. She stretched the chain toward a stake she'd driven on the far side. Two more measurements and the map would close. Then the water heaved. A long ridge of armored scales broke the surface. A river crocodile, wide as a fallen door, swung its broad snout toward her. Its tail cut a slow line through the mud. Holly froze. The chain slipped from her fingers and vanished under the water. Her wolf barked once and lunged along the bank, teeth bared. The crocodile turned toward the noise. Holly scrambled backward, fell, and crawled out onto dry stones. The chain was gone. Her rod floated away downstream. Her only tools were now at the bottom of the river. She sat in the mud and stared at the empty water. Then she stared at the crocodile, which had settled onto a sandbar to bask. It lay perfectly still. Its back was a grid of ridges, each scale square and even, spaced by nature better than her broken chain ever measured. Holly pulled out her notebook. She sketched the beast fast, counting the rows of scales, marking each one as a fixed unit. If she knew the true length of one animal, she could pace the river against it. No chain. No warped rod. Just a living ruler that held still in the sun. She worked until midday, measuring the crocodile's body against the far bank while her wolf stood guard between her and the water. She filled three pages. The angles closed. The blank space on her map shrank to nothing. That night she inked the river's far bank into place. The map was finished. But her chain and rod were lost, and no judge would believe a master map measured by a wild animal. She would have to prove her strange method worked. And the crocodile that gave her the numbers was still out there, waiting between her and every future crossing.