A few minutes later, Lupin felt a sharp pain in his back, and he quickly stuck the tranquilizer dart in his arm, wincing slightly. He allowed the sedatives to be fully injected into his body, before ripping the dart out and throwing it across the room in frustration.
Running to his bedroom door, he slammed it shut and locked himself in it, hoping that all of these barriers would prevent his werewolf form from breaking out. He then stood still in the middle of the room, twitching and grunting as he changed.
His pale blue eyes turned a bright, poisonous yellow, and the size of his pupils contracted to the size of a small bead. His limbs grew longer, his fingers stretching out and growing long claws. Lupin's skin turned into a dusty brown, and his face elongated until it looked like the face of a monstrous canine. His teeth grew sharp, foam dripped from his mouth, and he howled in pain as his spine bent, his tail grew, and his ears pointed upwards.
Finally, he looked like a tall, freakish mangy mutt standing on its bony hind legs, white foam dripping from his mouth and claws that could touch the ground if he'd let them hang.
Lupin sniffed the air to see if any werewolves were nearby, and howled, before charging at the door that contained him in his room. He scratched and kicked at it until he had made a hole big enough to force his paw-like hand through. He made an attempt to twist the doorknob (though, the door was locked) and instead of successfully opening the door he completely removed it. Stepping back, he kicked open his door and the whole thing fell to the floor, leaving Lupin in a cloud of dust that soon settled.
He scratched at the walls, that already looked like they had been abused enough, and knocked down pictures and clocks and tore up wallpaper. The tranquilizer dart seemed to have no effects on his behavior, he was still determined to escape and kill.
After having a fight with his mirror (Lupin won), Lupin ran to his boarded up door and slammed his body against it until it crumbled and allowed him to escape.
Scratched up and covered in splinters, the werewolf breathed in the fresh air full of potential prey, and ran into the darkness.