Okay, here we go. Sorry for all the exposition- this is the calm before the storm, believe me.

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Mary placed her hands on either side of her stomach and pushed in, the fat flowing into her body and settling in other places as her stomach shrunk. By the time she had reached her muscles, she struck a bizarrely hourglassed figure, fat from her breasts up and her hips down with a six-pack of muscled abs between them.
"Aside from the whole 'eating people' thing, this is kinda fun." She repeated to herself again. She felt a tingle in her arms and legs, and watched as the rolls of fat began to turn green and section off into tentacles, dropping from her and slithering off towards the corner her lair was in. Eventually she was left with nothing but the muscles, a statuesque figure that wouldn't be out of place in a top-tier bodybuilding competition.
"Wow," Mary said, admiring the way her clothes clung to her muscles. "Nice, but a little too much," She willed a little babyfat onto herself, smoothing out the hard edges of her features. She was content to be musclebound, but she didn't really want to look it so much.
"What to do, what to do..." Mary said as she looked around her apartment. Her eyes settled on the hole in Katie's floor, and she thought of her and Katie's plans to swap apartments. For all the trouble she's put her through, Mary thought, wouldn't it be nice if she could get it done for Katie before she got home? Resolving herself to her task, mary put her hair up behind her in a ponytail (Without having to actually touch her hair) and set to work.
Mary found with her new strength that any piece of Katie's furniture was as easy to pick up as a cardboard box. She giggled as she hefted Katie's television, sofa, and bookshelves with ease, her arms able to wrap around them entirely, sometimes twice if necessary, her grip as sure as cast iron as she moved each piece down to her apartment. As she descended the stairs each time, she commanded the lair cluster to slide underneath the next piece of furniture she had in mind and drag it to the doorway so it'd be ready for her to pick up as soon as she got back up the stairs. She kept an eye out for anyone in the parking lot in her short jaunts from her apartment to Katie's- even from a distance, a woman of Mary's stature carrying a kitchen table all by herself would seem dangerously out of place.
As the sun began to set and Mary finished up the apartment swap, she realized that in the hours she'd been carrying furniture back and forth, she hadn't even broken a sweat. Come to think of it, she hadn't felt the need to go to the bathroom since her change, either. Mary shrugged and chalked it up to The Flesh's unequalled efficiency. As mary sat back on the recliner-like blob in the corner of Katie's (Now her) apartment, she wondered if The Flesh had other medical benefits. Would she never get sick? Could she even get sick anymore? What about other diseases? Mary wondered if The Flesh could cure cancer, or it it was indeed a kind of cancer itself, needing to grow and multiply as it did. Mary had never been much for medicine- verdicts could be appealed in a way the life-and-death nature of medicine wasn't as forgiving- but her situation made her wish she knew how to study it. She'd be tempted to go ask someone- a biologist? A chemist? A Zoologist?- if she wasn't afraid of being confined to an airtight box for the rest of her life in the process.
"Well look at you," Katie said as she walked in, "Someone looks pleased with- wait, whoa..." she trailed off as she saw the result of Mary's labors. "How'd you do all this in one day?" She asked, hands on her hips and an impressed eyebrow raised at Mary.
"Easy-peasy when you've got guns like... these!" Mary said, dramatically flexing one of her arms and pumping up her bicep for added effect. Mary paused long enough to catch Katie's eyes pop wide, then returned to her normal shape. "How about you? You're looking good."
Katie smiled and opened up her jacket, showing off her normal-sized breasts. "Not one smidgen bigger," she said, doing a quick turn-around. "I think I can kiss tons-of-fun goodbye."
"Well good, good," Mary said, rising to her feet. "And how was class?"
"Fine, fine," Katie said as she set her bag down and headed into the kitchen. "You leave any food in here? I'm famished."
"Yeah, there's still stuff in there," Mary said as she followed Katie into the kitchen.
"I see you got rid of the milk," Katie siad, nodding her head towards the stack of pots in the sink as she opened the refridgerator door. "What'd you finally do with it?"
"Oh, that. Yeah, I just drank it."
Katie nearly dropped her yogurt cup as she looked over at Mary with a start. "Drank it!?"
"Well, yeah?" Mary said, shrugging. "Not like it's gonna do anything wierd to *me*..."
Katie shook her head as she opened the lid and stuck a spoon down into the yogurt. "I dunno, honey, piling wierd on top of strange seems like a recipie for nothin' good." She ate a spoonful of yogurt, then wagged the empty spoon at Mary. "And besides which, you drinking something that came out of my boobs is just out-and-out creepy, I don't care what you say!"
Mary laughed. "Well, it looks like the injection took, so we won't have to worry about it anymore, right?"
"God I hope so," Katie said, finishing off her yogurt and looking at her wristwatch. "Ah geeze, I've gotta get to work- I'm already behind a day since I didn't get to do any work last night."
"Well, I moved your desk and all your papers and books downstairs, so everything should be ready for you. Pretty easy since we have the same floor plan and all."
Katie nodded as she went to the door and hefted up her bag. "Oh, I've got your paper back, if you want it. Dr. Allen asked about you, I just told him you were sick."
Mary thought for a moment, then shrugged. "Just toss it. I don't think I'll be going back there anytime soon..."
"Aw, I'm sorry, honey..." Katie said as she opened the door.
"Don't worry about it, It'll get fixed eventually," Mary smiled.
"All right, see you tomorrow," Katie said as she backed out the door and shut it.
Mary managed the night without any more dreams, though she found her sheets and blankets unusall itchy. As wary re-adjusted her bedding for what seemed the hudredth time, she vowed to wash her sheets first thing in the morning and see if that helped.
In the morning, Mary heard Katie leave for school once again, but strangely- it took her a moment in her groggy state that she was hearing Katie through the tentacles closest to the hole in the floor. Mary re-focused her senses, bring her back to her immediate perceptions as she dragged herself from bed. She assumed, as she stripped her sheets and pillowcases from her bed, that if Katie had reverted or otherwish showed signs of her titanically-titted alter-ego she would have heard about it, likely through the floor at the top of Katie's lungs. She took the bundle of sheets into her bathroom, in the tiny little washer/dryer nook that sat kitty-corner from the shower, and dumped the load into the wash. As Mary unscrewed the cap from her detergent, she recalled her thoughts from last night. Could she get sick? MAry remembered the time she'd accidentally spashed a dollop of detergent into her mouth- just the taste of it on her tongue nearly made her vomit. As she poured the detergent, Mary stuck a finger under the flow for just an instant, tilting the jug back up and screwing the cap back on with her clean hand. As the washing machine filled with water, Mary brought the soapy finger up to her nose, giving it a sniff. She could smell the soapy detergent, the artificial "Mountain meadow" scent tickling her nose. Her lips parted, her tongue poking out just past her lips. Mary reflected on how dumb this whole idea was for a brief moment before dabbing her tongue with her finger, getting ready to spit at the first sign of distaste. To Mary's surprise, she tasted... nnothing. Well, not nothing. Almost nothing. It was a dull, bland sensation, but not at all unpleasant. She swallowed, and still felt nothing wrong. Feeling a bit of bravado, Mary sucked her whole finger clean of the detergent, but felt no ill effects of it. In a way Mary was unsurprised- she had, after all, eaten a good chunk of Katie's countertop only a little while ago. But people had eaten wood and glass and the like before, she'd seen them on TV. But laundry detergent wasn't just odd- in a human digestive system it was harmful. But apparently anything goes for The Flesh. Mary eyed the bottly of bleach on the shelf over the washer, suddenly tempted. Soap was bad, yes, but bleach- people have died drinking that stuff. But still the question nagged her.
"Just a sip," she said to herself as she reached for the bottle. "If the soap didn't do anything, this won't hurt."
Mary popped the cap of the bottle of bleach and raised it to her lips. The smell was unlike the detergent- this was acrid, caustic, a big flashing olfactory "NO" sign. Mary tipped the bottle further.
Nothing. Again. The same dull, bland taste, like The Flesh was instantly neutralizing anything it construed as harmful. Mary took a bigger gulp, determined to taste something, anything, trying to force her body to acknowledge the clearly insane nature of what she was doing. She got halfway through the bottle before she gave up, wiping her mouth with the back of her hand and feeling her skin absorb the droplets she had wiped from her lips.
"You really are indestructible, aren't you?" She asked, looking down at herself.
Mary ate what she could from her fridge, taking her growth in stride. It was her breasts again this time, though Mary was able to mitigate the effects by willing the tentacles out of her breasts when they were only around the size of beachballs as she ate. As good as it had felt to have the tentacles squirming out of her freakishly lage bosom, Mary wanted to try and keep herself from such heights again; she got the distinct impression that The Body could very easily take advantage of her in such situations. As the last of the tentacles squirmed out of her, returning her breasts to approximately their original size, Mary felt another kind of hunger pang; The Body needed to go into the woods again. She sighed and headed for the door, noticing that her Lair was beginning to encroach on her furniture again- she gave it a half-hearted mental shove back into the corner as she headed out the door.
Mary inhaled deeply. She'd been in the woods behind her apartment before, but only briefly, and never very far. There'd always been something or other that called more urgently for her time. Now, however, faced with the reality of needing to drop out of law school and sequestering herself away from other people (potential victims of The Body's aggressiveness, rather) she found the solitude without interruption. It was nice to just relax, Mary thought, pushing the circumstances of her freedom from her mind as best she could. As the early morning light dripped through the gaps in the heavy clouds, she took another deep breath, walking farther and farther away from the apartment complex. In a short time, she couldn't hear the cars on the road, not even the big trucks getting off the highway. Mary wondered why she'd never taken a hike back here before. She stood, head titled back, eyes closed, allowing herself to just let nature wash over her.
The reprieve was interrupted when Mary tasted something crunchy in her right foot. She looked down to see a line of ants being happily devoured as their trail went over her skin.
"You just have to ruin everything, don't you?" Mary asked as she looked down.