美国一黑社会组织在香港进行一场高科技实验，研制了R19“生长激素”，可使动植物的生长速度提高300-1000倍。正当实验成功之际，不料在实验中出现失误，突遭黑手党袭击，R19下落不明，一条变异的蟒蛇逃出了实验室。起初大蟒蛇一开始并不食人，还和一女孩成为好朋友，可该组织一心想消灭巨蟒，蟒蛇遭到高压电电击，片刻消失得无影无踪。就在他们得意忘形之际，一条更大的蟒蛇夺雾而出……

A research lab has developed "The Formula", a box that allows living organic material to grow hundreds of times its original size. Criminals invade the lab to steal it, but it's thrown off the side of the road. There it's found by a girl who decides it will be the perfect home for Mosler, the snake she has adopted. Mosler immediately outgrows the box, springing to the ground like a pile of novelty dog poo. Gang members see the girl and her huge snake frolicking outside and put two and two together. Mosler thwarts their first attempt to snatch her, but when they do succeed he goes on a rampage trying to find his friend