Wendy had eleven minutes to find a door that didn't exist on any map. Three weeks ago her brother slipped into the deep sector of the orbital station and never came back. She had followed him to this station six months after her own reassignment, and he had followed her up before that with no posting of his own. Now the deep sector was sealed to everyone. The next lockdown would seal it harder. She pressed her hand to a blank wall on the lower deck and found nothing but cold metal. The station intercom counted down the lockdown in a flat voice. Ten minutes. Wendy walked the corridor twice. Every hatch she found was welded shut or missing its panel. Her fingers shook. She had been searching for two days and had learned only one thing: the deep sector entrance was not where the public maps said. A man rounded the corner, dragging a heavy tool bag. Gray hair, thick glasses, a tool belt heavy with wrenches. Wendy had seen him before, always alone, always headed down. He was the old maintenance chief, the one who had kept the station running for thirty-one years. He did not slow for her. "You can't be down here," he said. "Lockdown's coming." "My brother's inside the deep sector," Wendy said. "I can't find the way in." Frank Dawson stopped. He looked at her for a long moment. "Nobody finds it. It's not on the maps. I built half of it myself." "Then you know the entrance." "I do." He checked the countdown on the wall. Eight minutes. "I'm going down to fix the cooling lines. Management says it can't be done. They're wrong." He hitched the bag higher. "Kids don't come back out of there." "Neither will you if the lines fail," Wendy said. "Take me. I'll help carry." Frank studied her Adidas shoes, her shaking hands. He grunted. "You'll slow me down." Then he turned and walked to a section of wall that looked like all the others. He knelt, pried a floor grate loose, and reached into the gap. Something clicked. A seam split open in the wall, low and narrow, a hatch no map showed. "That's it?" Wendy stared at the black opening. "That's it." Frank swung the tool bag through first. "Once we're in, the lockdown seals behind us. No coming back until it lifts. You understand that?" The intercom said five minutes. Wendy thought of her brother, alone in there for three weeks because she had come to this station at all. She dropped to her knees and climbed through. The hatch hissed shut behind them. The lock engaged with a deep, final thud. She was inside the deep sector now. So was Frank. The way out was sealed, and her brother was somewhere in the dark ahead.

The hatch's lock still hummed behind them. Wendy stood in the dark and listened to Frank set down his tool bag. His work light snapped on. It showed a low tunnel, pipes overhead, and three branching halls. She had thought finding the entrance was the hard part. Now she saw she was wrong. "Which way did my brother go?" she asked. Frank knelt at a cracked cooling line. He did not look up. "I came to fix these lines. That's the job. Not your brother." "You said kids don't come back. You know this place." "I know the pipes." He pulled a wrench from his belt. "The rest of it changes. Halls move when the station shifts. I'm not walking you into that." Wendy stared down the three halls. Each one looked the same. Without Frank she had no map, no light of her own, no idea which turn her brother had taken. Her chest went tight. She had sealed herself in for nothing. Then a low bark echoed up the middle hall. Frank froze with the wrench halfway to the pipe. A black dog trotted into the light. It was thick and muscled, with bright green eyes and a tag swinging at its throat. The tag said Loki. The dog stopped, looked at Wendy, and barked again toward the dark. "That's my brother's dog," Wendy said. Her voice broke. "He brought it up with him. It followed him down here." The dog turned and walked a few steps into the middle hall, then looked back. Frank set the wrench on the pipe. He watched the dog, then Wendy, then the dog again. "Animal's been eating something down here," he said. "Means someone's feeding it." "Then he's alive." Wendy took a step toward the hall. Loki wagged and moved ahead. Frank swore under his breath. He stood, slow, one hand on his bad knee. "The lines can hold another hour." He hitched the tool bag onto his shoulder and pulled a folded paper from his coat. It was hand-drawn, creased soft, marked with routes in faded ink. "I keep my own map of the parts that don't move. It's not much." Wendy looked at him. "You're coming." "I'm following the dog," Frank said. "You're following me. Stay close. If I say stop, you stop." He held the light out down the middle hall. Loki was already trotting ahead, tag jingling, sure of the way. Wendy fell in behind Frank. For two days she had been alone with a wall. Now she had a light, an old man who knew the pipes, a hand-drawn map, and a dog that knew her brother's scent. The three halls no longer scared her. Only one mattered. They walked into the dark together, and the middle hall swallowed them.