Author's note: Two updates in one day!
The smoky red light from the flare in Dean's hand would last 15 minutes, according to the label. Whether that would hold true in the mysterious darkness was another matter, one which he didn't want to have to find out about. Priority one was finding Sam, closely followed by putting down the thing that took him, and making it permanent. No way this thing is going to trash the place less than a week after we got it, Dean thought grimly.
At the bottom of the stairs, the first column of the library had a stain on it. Dean crouched down to inspect it more closely. Blood. His jaw tightened. Sam's blood, almost certainly. He stretched out his arm to extend the light of the flare, and saw more smears of blood. The thing had dragged Sam this way. Dean picked up the pace, following the intermittent trail. It led to a door Dean hadn't explored beyond before, one that when opened revealed a set of wooden stairs leading down to somewhere that smelled of dust and dampness. "Great, a freaking cellar," he muttered to himself. He took a deep breath, and then started down the stairs.
The thing paused, drawing back from Sam. It went very still, very silent, and Sam heard it sniffing the air. He could see it in his mind's eye – a nebulous form, but one that had sensed something, and was now listening intently. A moment's pause, and then the thing moved, scuttling away. Sam tried moving again. His body tingled all over, and sensation was dulled. He could barely move, let alone be any kind of use in a fight situation. Can't even get up, he thought in frustration. With an immense effort, he slid sideways. If he could even just drag himself across the floor, maybe he could fool the creature into thinking he'd gotten away when it inevitably returned. He started moving with difficulty. In the darkness, he imagined that he saw a faint red light. His mind was likely playing tricks on him, but he dragged himself in that direction anyway. It was better than aimless movement in the dark.
Dean reached the bottom of the stairs, and strained his eyes to the limits of the light. Sam had to be down here somewhere, but he was sure the thing was too. "Come and get me, you son of a bitch!" he yelled as loud as the smothering darkness would let him. He was answered by being knocked bodily to the ground as the thing sprang from the darkness at him. The flare was knocked from his hand, and it rolled onto the ground, spinning in a circle. Semi-illuminated in its slowly spinning red glow was a hunched, oil-slick black animal the likes of which Dean had never seen. It was on all fours, but the front two limbs ended in twisted hands rather than paws, each finger sporting a barbed claw. Its spine was ridged, and its body was lean muscle. Its ears were large and pointed, and it had a short, almost flat muzzle. The eyes were tiny black points, and the nostrils were wide. The thing snarled, displaying a set of sharp and pointed teeth, and the flare went out. Dean lifted his gun and pulled the trigger, emptying the entire clip into the darkness where the creature had been. It yelped, and a flurry of movement told Dean that he might not have killed it, but he'd at least managed to hurt it, and scared it into running. He pulled out his second flare, breathing hard, and set it alight as he got to his feet. "SAMMY!" Stepping forward, he started searching for his brother, not knowing how long it would be before the creature returned. A dragging noise caught his attention, and he moved that way quickly. He nearly tripped over Sam – bleeding, dirty, crawling on the ground. "Holy crap! Sammy, I got you." He set the flare down, and tried to help his brother up.
"Can't walk," Sam said through gritted teeth. "Thing poisoned me."
"I'm gonna get you out of here even if I have to break my back carrying you," Dean said firmly. He heaved Sam up as best he could, most of the younger man's weight on his back and shoulder. "Can you hold the flare?" he asked. He grabbed the still burning tube from the ground and pressed it into his brother's palm.
"I think so," Sam said, doing his best to tighten numb fingers around it.
"Keep it out of my way and if you see that thing coming back, shove the burning end in its damn face," Dean said. With an effort, he straightened his legs and back, and dragged his brother up the stairs and through the door. The two of them collapsed onto the floor, and Dean kicked the door shut with a foot. "We need to find out if there's more than one way out of that freaking cellar. You seen any blueprints for this place?"