Jenny grinned a little as they opened it up. She couldn't believe that had actually worked, for attendants at the zoo they were way too easy to fool. That had been a fake combination that he had set up in the event that something like this happened. Now it was just a matter of watching to see what happened. She swished her tail a little in expectation.
When the safe went fully open, the attendant looked in expectantly, not noticing the light gas coming out of the door. He reached forward and grabbed the object inside, not noticing that fur was growing up his arms as his hands turned black and started to harden. He grinned as he held the item in his hands, it looked important enough, but he barely noticed that the transformation was overtaking him.
Jenny could feel the changes overtaking her own body, she didn't change much physically but she could feel her genitals changing, the vagina pushing out to form a set of equine balls and a sheath as she... now he smelled the changing scent of the man in front of him. The trap had been to cause a gender swap that would induce an immediate heat in mares.
When the attendant finally realized what was happening, it was too late as his pants had split apart and he was struggling to stay upright as Jenkinis approached, his newly grown horsecock sliding out of its sheath as the transforming mare subconsciously raised her tail. The attendant knew that their fate was sealed as they felt the heat growing in their loins as it formed into a perfect vagina that winked at the stallion.
Jenkins moved closer and paused a moment. Sure he could take her now, but at the same time it would be much better revenge to let her experience the same unbearable heat. So, what should he do?