Michael and Vivian watched as the former mother and father advanced towards their children. Before they got too close, a remnant of the parents' former humanity presented itself. Both wolves stopped, snarls turning to looks of confusion.
Michael seized this opportunity to grab his sister by the arm, and pulled her away from the advancing wolves. Shaken from her reverie, Vivian chased after her brother, sparring one look back at her former parents and the zoo staff forming behind them.
"Well, what are you waiting for? Get after them!" shouted the zookeeper.
With that the wolves charged, closing the distance with their former children fast. Michael, hearing the approaching beasts, pulled Vivian towards a low fence surrounding the zoo and began climbing over it. "Come on Viv, they're almost on us!" Michael shouted back at his sister.
Michael was in the process of helping his sister over the fence as his former mother surged towards them and lunged at Vivian's dangling leg. Driven by a surge of adrenalin, Vivian threw herself up and over the fence as the wolf clattered into the area her leg had been only moments before. Both children, taking advantage of the obstacle the fence offered against the wolves, quickly ran further into the zoo. The two ran from building to building, trying their best to outrun their pursuers.
After what felt like hours, the children finally collapsed in a heap in a deserted building. They had reached a quieter area near the centre of the zoo, their pursuers focussing their searches around the exits. Once he had caught his breath, Michael glanced around the room they were in. The shelves on the walls contained numerous clear tubes and other scientific equipment, along with identification numbers and notes. The tubes contained clear liquid, referred to as some form of antidote. A sharp gasp from behind, distracted Michael from his observations.
Turning around, he saw his sister studying a scratch on her foot. His gaze, however, fell on the shape protruding from her groin.
"Michael, something's wrong! I think I'm changing as well. You need to get away."
Michael made to get away from his changing sister before his gaze was caught by the tubes again. He grabbed a vial and tossed it at his sister. "Try drinking this Viv. I don't know if it will help, but it's worth a shot."
Vivian quickly took a drink of the vial's liquid. "Well it was worth a try, but I don't think its work -" Vivian was interrupted as her growing penis shot to full attention. A moment later a wet spot had formed on her jeans at the tip of the appendage. "What was in that tube. I feel weird hng."
Vivian was cut off as with a groan her new appendage spurted cum through her jeans. Michael made to run from the room before he saw the jeans bulge diminishing in size. His sister groaned again, spurting another load over the floor. She grabbed a nearby chair and with a last thrust expelled her remaining cum onto a pile of paper and notes. Vivian turned back towards Michael, her appendage now gone. Michael looked in shock at his sister before coming to his senses.
"Quick, grab as many vials as you can carry."
The two grabbed a number of vials each and ran into the adjacent room, finding themselves in the...