Nevara Goldvren came off the ridge with an empty sled and a bull caribou six paces behind her. The bull had green hide and antlers cased in ice, and it had chased her and her partner off the kill an hour ago. Her partner had run south toward the pass. Nevara had run north, toward the frozen creek bed no map showed, because the black flame dragon had been seen there twice and she meant to bond it before the season closed. She stopped when the bull stopped. She counted forty steps between them. The Queen's army did not send frost hunters after caribou; it sent them after weather and tracks and men who deserted in the cold. Nevara was the best tracker in the third battalion. Commander Aldric had stopped assigning her partners after her first winter and had never said why. She knew why. She wanted his rank and two above it, and she wanted the dragon nobody else would chase, and she carried a metal box against her ribs that held every note she had taken toward both. The box was lined with bone chips from the six field reports and tied shut with sinew. Inside were pages copied word for word from the one man the dragon had spared. He said the dragon had looked at him like it was waiting for him to choose something. Nevara had a theory about what. She had tested pieces of it on wolves and on men in the barracks who did not know they were being tested. She needed the roost to test the rest. The bull lowered its antlers and swung once, slow, marking her. She stepped sideways off its line and it let her. She followed the creek bed north instead of south. Two hours in, the creek opened into a clearing, and at the far end of the clearing stood an arch of dragon vertebrae half-sunk in snow, bleached white, taller than three men. Scorch marks blacked the inside curve. Bootprints from no boot she recognized went under the arch and did not come out. Beyond the arch the ground rose into a cliff face pocked with cave mouths, and the air above the caves shimmered the way air shimmered over a forge. She sat behind a drift and opened the box on her knees. She wrote down the arch, the scorch, the count of cave mouths, and the direction of the shimmer. She wrote the date. She closed the box and tied it. The roost was found. Her partner was gone, her official route was two days east, and her mother's letter was folded in the lid telling her not to write back if she came here. Nevara ate a strip of dried meat and watched the caves until one of them breathed.