I'm just going to drop this here while it's fresh in my head. I'll probably come back to it later.
The storm came out of the west like a wall of darkness, pushing a wave of dark clouds ahead of it. Advancing relentlessly, it swallowed the mountains and crawled down the plains.
Jacob Maddox stood on his porch and watched it come. It was an amazing thing, not so much a front or a system as a single, massive storm. A hurricane, but forming over land. A typhoon... He could see the leading edge of it, a clean line where the rain began - and behind the rain, darkness.
Behind him, Buster nosed the door open and made a break for the yard. "Hurry it up, mutt!" called Jacob, fondly exasperated. He turned back to the house to get a towel; there was no way on Earth that the dog was going to finish his business before the rain hit, and he didn't need wet paw-prints all over the house.
He heard the rain hit the edge of the porch as he pulled open the door, heard it march steadily across to the other side of the house. The transition between not-rain and rain was so precise that he could actually follow its progress by sound, as the edge of the storm crossed from west to east. As it reached the far edge of the roof, he heard something else: a faint cry from Buster, almost drowned out by the drumming of the rain.
Turning back, Jacob saw that Buster had rolled over. For a moment, it looked as if the mutt were just rolling around in the mud, but no: there were too many legs. And even in the darkness and the rain, he could see that the body was too long for the half-collie mongrel that had been the family dog. It wasn't rolling, either; it was rippling its way back towards the porch like some giant, furry caterpillar. Sweet Jesus, no...
He stumbled back into the house, heading for the bedroom. His mind was on the pistol in its drawer beside the bed. As he passed the living room, Sara called: "Honey?" Behind her, he could hear the announcer on the television: "...lost contact with everything behind the storm front. F.E.M.A. is urging everyone to stay indoors until the storm passes or we know-"
The power went out.
Jacob kept going, slowing only slightly. After ten years of living here, he knew the floorplan well enough to navigate blind.
Then the floor twisted under his feet, and he stumbled. He hands came down own something ridged and irregular: roots? There was something soft and mossy over the top of it, but it was not the carpeted floor he'd been walking on a moment ago.
The bedroom was just ahead, so he climbed back to his feet. His knee twinged, but held; he hadn't twisted anything in the fall, thank God. The substance of the house might have changed, but the layout was still the same; Jacob stepped through the doorway and slowed. Two careful steps, and he found the bed; it seemed to be unchanged. He circled it, found the night table - also unchanged. The gun was still in it, and so was the flashlight.
He switched it on.
The walls were layers of plant fiber, as if they'd been completely grown over... or as if the house had never been built, and had been grown instead. It was still their house, though: the pictures on the walls were unchanged, the furniture untouched. What the hell was going on?
Flashlight in one hand, pistol in the other, Jacob retraced his steps. As he neared the living room, he heard Sara ask: "Buster, is that you?"
A sudden fear flashed through him, plowing into and tangling up with everything else that was spinning around in his head: a vision of the thing that had been Buster inching towards Sara in the darkness. "Hang on, Sara," he called back, and stepped through the door.
The flashlight threw a circle of light on the far wall, which was now as thoroughly fibrous as the rest of the house. It touched the darkened television, swept over the back of the couch, and lit up the mantle above the fireplace. He tilted the light down so as not to blind Sara, and moved cautiously around the couch.
Buster was now a knobbly, golden-furred snake, stretched from the door to the corner of the couch. It wasn't quite within reach of Sara yet, and it didn't move like a snake: instead of slithering, it flowed in a series of vertical ripples, gathering and extending. "Buster?" called Jacob.
The... dog... stopped, and its head twisted around atop a foot of furry neck. It was looking at him, head slightly cocked. The gesture was achingly familiar. Then its mouth opened, and instead of the familiar pink tongue, a bundle of thin red wires extended. It made a sort of urf sound, a wounded echo of the old familiar bark of greeting.
"Buster?" asked Sara, and suddenly scooted away across the couch. Her voice was loud and high.
"It's okay," said Jacob, forcing the words through a deep certainty that he was lying. "C'mere, boy."
Buster wound around and began its horrible limping flow towards Jacob.
That was when the roof caved in.
Whatever was happening outside, it wasn't done yet. Jacob stumbled back, and the light strobed wildly across the room. He caught flickering glimpses as he steadied himself and tried to rise: slim, branching tentacles prying apart the rippling vines of the roof; Buster, twisted back, barking wildly as he had when he was still a dog; dark rain pouring in to cover Sara as she fell out of sight in front of the couch. It was the tree, the big old oak in the front yard: transformed, animated, and thrashing wildly.
Then a splash of rain fell across Jacob's outstretched hands.
For a moment there was only the cool touch of rain. A moment later it felt as if he'd thrust his hands into a pot of boiling water. The gun and the flashlight twisted in his hands, and he tried to drop them as he threw himself backwards towards the bedroom.
Neither item left his hands. The flashlight seemed to be dissolving, but the light was still there: it seemed to be flowing into his hand, without bulb or battery, until his hand itself was glowing. He barely saw that, though, before the gun twisted and bloomed... and then clamped down in a block around his hand. A moment later it had entirely surrounded his fingers, turning his hand into an oddly-shaped lump of metal.
The pain died away into tingling, as if he was suddenly getting his circulation back.
His left hand was intact, but glowing brightly from his fingertips to a point about two inches past his wrist. Softer traceries of light were visible beneath the skin, going almost to his elbow; they seemed to follow his blood vessels.
He looked up as Buster wiggled towards him. A second exposure to the dark rain hadn't changed the dog any further, but behind him...
Sara had been drenched by it, and she wasn't Sara anymore.
He didn't shoot her, didn't shoot the skeletal, eight-foot tall humanoid as it crept forward, hunched over to keep its head beneath the ceiling. Buster seemed to have retained something of his memories and personality; maybe Sara had too. So Jacob stepped back, and gestured with his glowing left hand for them both to enter the bedroom. Buster slipped easily through the tree-trunk doorway; the thorns on Sara's exoskeleton tore chunks out as she squeezed through. She pushed the bed back to make more room, and huddled down between it and the inside wall. She tried to speak, but what came out was a horrible, unintelligible screech.
Buster curled up beside her. Jacob settled in the doorway, watching the lashing tentacles as they tore up the rest of the living room and pulled down part of the front wall. There was light outside the hole, and similar light outside their bedroom window, but Jacob couldn't see where it was coming from. The window glass had become a soft, greasy membrane; and he couldn't get close to the whole for fear of what had once been a tree.
They waited for hours in the darkness, and eventually - inevitably - they slept.