The horses were all fed, watered, and brushed down. Tom was about to close up the stable for the night when Lucy walked in. She was a beautiful, demanding blonde who loved horseback riding. She was 18 now, but Tom knew her mother would never allow her to be in a relationship with a mere stable boy.
Lucy approached Tom, nervous but determined. She had a crush on him for awhile. He was handsome, very fit from his physically-demanding job, and tanned from his work outdoors. He wore his dark hair almost down to his shoulders and it reminded Lucy of a horse's mane. She met Tom with a kiss. It was not their first. They had held hands and kissed on several occasions before, always secretive about such behavior. Lucy knew Mother would never approve of that, and would be absolutely thunderous with rage if she knew why Lucy was out in the stable now. Lucy pulled Tom into an empty stall.
"Father is away on business and Mother has gone to bed early," said Lucy. "There is nobody to catch us. I want to ride."
"But the horses..." Tom began to say, but Lucy cut him off by letting her dress fall to the dirt. She wore nothing underneath.
"I want YOU to ride ME" she said, kissing him more forcefully this time. She could feel his erection through his pants. Then Lucy flung herself back onto a pile of hay, and spread her legs. She loved horses so much the smell of the hay and the horses turned her on more. That's why she wanted to loose her virginity here.
Tom eagerly pulled off his shirt, but even as he did something didn't feel right. He was aroused. Almost too aroused. He could smell Lucy's arousal. The scents of the stable grew stronger. He removed his boots then struggled with his pants. They seemed caught. Finally he got them down and then struggled with his boxers. Then he stared at what had happened to his manhood, struggling to comprehend it.
Lucy also immediately recognized what she was looking at. She sat up and reached out to touch it, having trouble believing her eyes. "Have you always had a horse's cock?"
In response to Lucy's touching his newly engorged penis, Tom let out an uncontrolled sound he immediately realized was like a horse's whinny. Then he felt something at his tailbone. He reached back to brush it away, only to realize what it was. Tom turned and shook his tail.
"I'm turning into a stallion!" exclaimed Tom.
Lucy wasn't sure if it was still physically possible, but now she wanted Tom to fuck her more than ever.