James backed away from his sister as she began to change more. She grunted as her cock busted through her zipper. It was clear over her panties as she grabbed it. If it weren't for her waist growing her pants would've fallen off when her cock surged larger and broke the button. Her now hairy sack hanging out as her panties snapped.
Hearing a deep moan James looked over at his mom and Ben. His mom's neck was now thicker and had a bulge on it. Her pectorals grew as her breasts vanished. They then grew even larger breaking her useless bra in the process. Margret could hardly care as she cummed, the goo splattering across Ben's face.
Ben had also changed as a result of this fucking. His mustache fell off one strand at a time as did the rest of his body hair. his ass then inflated to give him a pear shape to his once lean body. "everyone snap out of it!" James said. he tried to get his mother off of Ben but it was like moving a rooted tree. Luckily this did make Margret a bit lucid and she backed away from Ben.
"no Margo don't go," Ben said as he licked the cum off his face. His face softened as he rubbed his empty crotch. Now that Margret was on the other side of the room her mind returned to her still somewhat fogged. "James what hap... UGH," she grunted as another shot of cum came out of her cock. A goatee formed on her now chilled chin. Her lips thinned and her nose grew. As her eyebrows grew thicker James explained.
"Mom there's something in the air. I think it's around Ben" James said pointing to the former man. If Margret had been fully aware she probably would've been horrified at what happened to her assistant. Instead, she watched as a vagina opened up on his crotch and he massaged it. "Mom, it's my turn" Sam rushed past him and kneel in front of her mom's penis. Her leg muscles tore through her pants as her shirt rode up her growing torso.
Margret could feel deep down this was wrong but could barely say anything because it felt so good "S-Sam... don't... do it... Do it now!". Margret moaned as her daughter sucked her off. Hearing a door slam he turned and saw Ben was gone. A feeling of dread shook James to his very core. Meanwhile, the spirit watched the events unfold. It was shocked when even the scent it made that one human emitted didn't affect James. Perhaps it was due to him accidentally disturbing it. It could be he was just extremely resistant. If it could sigh it would. Instead, it followed Ben. James was no fun until he succumbed to its power.
Back in the lab James futilely tried to stop his mother and sister from screwing with each other. Margret moaned as her shoes bunched up before exploding off her manly feet. Sam meanwhile was rapidly catching up to her moms figure. After filling her mouth full of cum again Sam swallowed it. With the scent dissipating both of them slowly realized what they had done. "Sam no" Margret covered her mouth due to the deep voice coming from it.
Sam looked down at her long manly legs and feet. Everything from her new abs down was covered in hair and muscles. Instead of feeling upset, Sam felt joy at her new body. She hid this from her family as she did not want them to think she was crazy. "it's okay Mom" Sam got up and saw the hunk her mom had become. Oddly enough this didn't turn her on anymore. Instead, James's breasts made her flaccid member stiffen again.
"Sam control yourself," Margret said. She did not want her daughter to fall any further. She then noticed like Sam she didn't have any pants or underwear anymore. She then spotted her ruined jeans along with a silhouette of someone. the cum outlining made her remember whose breasts she had wedged her cock between. "wheres Ben" she asked. She ignored how a thought said it was hot to cum. "he left earlier. I don't know if he did so with a clear head though" James said while sitting down. First his coworkers then his family and now his mom's assistant. He couldn't figure out what was going on. It didn't seem to be airborne otherwise he would've been changed like Linda and Carla.
Sometime later his mom sat down on the stool next to him with the jar in hand. "we'll I've done some testing with this and it seems to be normal cum. I even tested the DNA and it came up mine. However, the chromosomes showed male markers instead of female ones." Margret was doing one of her talks. Whenever it happened both her family and classes knew to let her finish before interrupting her. "I did find some foreign marker surrounding it though. Whatever it is it's not anything science has discovered yet" She sat down the jar and hugged him. James returned the hug however he felt his mom's cock poke him.
The spirit had come back after some 'fun'. It saw Margret almost fully a man, explaining the changes. If it had eyes it would roll them. Science has bored it since it was first founded. An alchemist used 'science' to trap the spirit after he turned his girlfriend into a bull. After that it was trapped in that box, only able to change those around it in subtle minute ways. Thankfully after centuries, it had been freed when one of those office workers set a heavy box on its prison. All it needed was the hairline crack to escape. It then showed those humans that it was the most powerful transformation spirit.
The wisp then realized it wasn't bored of science it hated science. If anyone figured out what it was then it could be put in a container it could break out of or even use its powers. It phased through her right as she hugged her son. To its joy, his 'mom' pushed him onto the table and slammed 'her' cock into his pussy. It was amused when his sister joined in and plunged her cock into his mouth right as he was telling them to stop. Unfortunately, the will of the young man seemed strong as he refused to succumb to its powers. His family on the other hand delivered a large amount of cum to his mouth and pussy.
Soon it could do more 'extreme' changes to them like the others.