For a moment, Jackson had considered beginning the trek back to the truck, but his gut told him to check his subject. It was supposed to be a slow burning process, at least on paper, but this was clearly no ordinary animal to begin with.
A haunting whinny from over the hill confirmed his gut, and with quick steps he began jogging to the mare. As he topped the hill, puffing all the way, his eyes widened under the mask, and he gasped. Stopped dead in his tracks. She was trembling in the grass below, already mutating fast. With sharp breaths, he tried to calm himself as he approached, hearing the awful crackling noise as her flesh and bone shifted in the moonlit night. She let out another pained whinny, and threw her head back in agony. He watched with near disbelief as the process played out, seeing her front hooves beginning to splinter into stubby fingers. Her hindquarters shrinking rapidly, her chest pulling in.
He couldn't imagine how it felt, and was too dumbstruck by actually seeing it happening to think much else. Her back legs began to elongate rapidly, her hips were popping and crackling. He watched in amazement as she seemed to lose bulk quickly, shrinking in proportion and weight. Front legs snapped, neck pushed down, body broadened. Her torso was now slim and less animalistic. She was breathing intensely, raggedly, but refused to yield. The snapping of her bones was mixed with the awful pulling of her shifting flesh and muscle. Her backbone became visble through a skinnier back, her thighs popped into a bipedal stance, and her humanoid torso developed shoulders on which her long humanoid arms were still planted on the ground. Her neck thinned, her face shrank. She opened her eyes for only a moment and he could see the spark of intelligence forming behind them.
He stepped towards her, slowly, as it began slowing. When he reached her, she was close to done, and she finally collapsed onto the grass, exhaustion taking hold. Her form shivered from the massive transformation, and he marvelled at the humanoid and still somehow equine form lying before him. He kneeled down, her new hands rising to grip the sides of her head, and gently placed a hand on her back.
The mare's head rose sharply in the darkness and her haunted eyes glared back at him, blinking in the moonlight.
"H... Help. Help me." She said raggedly, inhumanly. Voice feminine but rough. She struggled at once, trying to turn and stand, but she was clearly exhausted.
"Easy, easy!" Jackson whispered sharply. "Just rest for a minute. Keep breathing."
She sat up, the swell of her fully feminine chest visible under the moon, and rubbed her rough mane with unfamiliar hands, staring down at herself.
"What is this?" She asked in confusion. "What's happened to me? I remember a light. And..."
Quite suddenly, the mare kicked away from Jackson, frantically, and struggled to stand. She was unable to do so, knees to weak to support her weight, and she collapsed again several feet away.
"You!" She pointed accusingly. "You did this to me! What did you do to me?"