Ranger Brody, with the help of his nephew and niece, is preparing to open the brand-new campground for the season. Everything is in order and the camp seems peaceful until a giant rat, mutated from multiple dumping of toxic wastes, begins killing the campers and rangers.

在明尼苏达州北部的“边界水域”中，六个老朋友之间的周末露营之旅在神秘的环境下死亡后变得悲惨起来，随着他们企图在本集团内揭露杀手，引发进一步的动荡。