Faye had always been short, and she hated it. Even Mary at her petite 5'3 was taller than her. She had always resented the lucky people, the tall people. She secretly desired to be bigger, the tallest one in the room. So when she had the chance to get bigger she wanted to go all the way. That's why she drank the contents of the vial twice - she wanted to be the big one for a change.
It didn't take long for the vial to take effect. Faye felt a searing pan building at base of her spine. Suddenly, she felt an explosive growth expand from her sacrum, destroying the tight leather pants she was wearing. A large mass was extending from her back lengthening and gaining girth at a seemingly exponential rate. And Faye felt every bit of it. It was the most intense pain she had ever felt in her life. After a few minutes, but seemingly hours in her mind, the growth abated and Faye turned to look at the results of her handiwork. A large black tail extended from her back, nearly 16 feet in length, and two feet at its base. Along the length of tail were long thin spikes, almost as long as her arm.
"Woah, "said Faye shakily." You didn't tell me it was that intense." She turned with difficulty and tried to feel her tail. She tried to move her tail and was disappointed to see that it was unresponsive, sort of like a limb that had fallen asleep.ten
"You wouldn't have listened to me if I did. And now its too late, "said Mary with an eerie calm. Faye turned to look at her with difficulty. Her large tail made it difficult to maneuver. She felt a little like a turtle stuck on its back.
Faye saw that Mary had continued to change during her transformation. Mary's abdomen was now covered on scales, extending to just below her breasts. Her lower abdomen was larger with a wider girth, but leaner seeming to be made entirely of muscle beneath the scales. She still had a nice hourglass figure, with a tight flat stomach. She started to walk toward Faye, with angry look on her face.
Faye felt a little helpless in her current state, and was intimidated by Mary's new physique and mobility. "Relax, " said Faye with an uneasy smile. "We can always reverse it."
Mary leaned close to Faye's face as she lay on the ground. "You better hope so." Mary then walked past Faye to the box, and began searching for the human vial. "And we better find the cure soon. My changes seem to be accelerating, and the pain just seems to get worse each time. And with how much you took..."
Faye guffawed. "I'm not worried. I can take anything you can take, even if it is at twice the pain."
Mary turned and smiled. "But you didn't take twice the dosage. You see, I only drank half the vial, and got this big. You drank two whole vials, essentially four times what I took. I shudder to think what kind of monster you are becoming."
Faye paled. Her tail felt odd, like a pain and pressure was building. "Mary, why didn't you warn me?" she said with a twinge of fear.
"I tried you idiot," said Mary angrily. "Now shut up and let me save us both."
"Don't call me an idiot, "said Faye, glumly, almost like a small child.
Mary rolled her eyes and continued looking. Her back and shoulders hurt. She knew the next phase of her transformation would begin shortly. She had to find that vial quickly, for both her and Faye's sake. She was running out of time.