The homeless man wanders into the woods and he's chased by the vampire hummingbirds when he stumbles onto one of their nests. He hops onto one of the creatures that are wandering through, which takes him straight to the laboratory, laid aside to use him as a first test subject.

The hummingbird that carried the homeless man dropped him at the castle door. Now the man sat caged in Raven's crowded laboratory. His name was Marcus Donnelly. He wore a torn jacket and red sneakers, and he gripped the bars with both hands. Raven Nightshade stood at her workbench, holding the first syringe. The green fluid inside it would begin everything. It would turn this frightened man into her first demon. But Marcus thrashed and kicked. She could not inject him without spilling the dose or losing him. "Hold still," Raven said. "This won't hurt long." Marcus screamed and rattled the restraints. One leather strap tore loose. His arm swung free and knocked a beaker off the cart. Glass shattered across the stone floor. Raven stepped back, the syringe raised high. If he broke the other strap, he would run, and she would lose months of work. A cold voice spoke behind her. "You're doing it wrong, girl." Raven turned. Corporal Silas Graves stood in the doorway. He was her assistant, bound to this castle long before she arrived. Little flesh clung to his skull, and red light burned in both eye sockets. An old blue army coat hung on his bones. The demon inside the dead soldier had helped her build this lab. She hated needing him. She needed him anyway. "He won't hold," Raven said. "I can't get the needle in." Silas crossed the room. His bare bones clicked on the floor. He leaned close to the cage and stared at Marcus. The red glow in his eyes brightened. Marcus went quiet. His arms dropped. His eyes glazed over, and his head sagged against the bars. "Fear feeds me," Silas said. "I drank his. He'll sleep now. Inject him fast." Raven did not wait. She reached through the bars and pressed the needle into Marcus's shoulder. She pushed the plunger. Green fluid vanished into his arm. She pulled the syringe back and stepped away, breathing hard. For a moment nothing happened. Then Marcus shuddered. His skin darkened to a deep purple. Thin horns pushed through his gray hair. On his belly, under the torn hoodie, a glowing symbol burned bright, a red circle crossed by two lines. His eyes snapped open. They were not human eyes anymore. Raven smiled. The virus worked. Her first demon lived. Then the demon tore the cage door off its hinges. It flew across the lab and crashed into the wall. Marcus rose, taller now, his new muscles straining his clothes. He looked at Raven. He looked at Silas. He did not look grateful. "It worked," Silas said. "But you gave it power and no leash." Raven backed toward her workbench. The thing that had been Marcus took one slow step toward her. The symbol on his belly pulsed brighter. She had made her demon. Now she had to survive it.

The demon took another step. Raven's back hit the workbench. Her hand found the empty syringe, useless now. The thing that had been Marcus Donnelly flexed its clawed hands. The red symbol on its belly pulsed like a second heart. She had built this creature. She had no way to stop it. "Silas," she said. "Do what you did before. Drain its fear." Silas Graves stood by the door, bones still, red eyes fixed on the demon. He did not move. "It has no fear left, girl. I cannot feed on a thing that feels none." His jaw clicked. "You made it too well." The demon lunged. Raven dropped behind the bench. Claws raked the wood where her head had been. She crawled under the apparatus, glass crunching against her knees. The creature smashed the bench aside. Pipes burst. Green fluid sprayed across the stone. "It will tear you apart," Silas said. He had not stepped forward once. "Your serum gives power and no leash. I warned you." Raven's hand closed on something hard under the overturned cart. A book. Thick, bound in cracked black leather. She had never seen it. Silas must have set it there. She yanked it open while the demon tore through the far wall, hunting her by scent. The pages were covered in symbols. One matched the mark on the demon's belly exactly. A red circle crossed by two lines. Below it ran three lines of harsh, angled words she somehow understood. "Read it," Silas said. His voice was closer now, low and steady. "The serum is the match. The book is the leash. I kept it for the day you failed." The demon found her. It wrapped one hand around her ankle and dragged her into the open. Raven twisted, held the book up, and read the three lines aloud. The angled words burned her throat raw. The symbol on the demon's belly flared white. The creature froze. Its grip on her ankle loosened. Its head bowed. The red glow in its eyes dimmed to a dull, obedient ember. Raven pulled free and stood. She was shaking. The demon knelt on the broken floor, waiting. Watching her. Waiting for a command. "It hears you now," Silas said. He finally crossed the room, bones clicking through the spilled fluid. "Speak the mark, and it obeys. Each symbol has its own words. Each demon, its own leash." Raven looked at the book in her hands. Hundreds of symbols filled the pages. Hundreds of leashes. Enough for every person she planned to change. The serum alone had almost killed her. Paired with this, it would not. "Stand," she told the demon. It rose. "Guard the door." It went. Raven wiped blood from her lip and smiled. The virus worked. Now the virus could be controlled. She had the serum, and she had the book. She needed more subjects, and a bigger dose. She turned to Silas. "Bring me another."