While hunting for deer on a cold October afternoon, Mark Bryant encounters strange bat-like creatures attacking a wagon train. When the creatures kill a family in a covered wagon, Mark rescues a young woman and gets her to safety just as a violent, severe storm advances across the Nebraska Plains. Repelling the attack, they are astounded when the creatures disappear into a storm. While on the way back to Mark's home where he wants to check on his family, they meet a man, Marvin Skaggs offers to help them. When they arrive at Mark's farm, they encounter more of the creatures. Mark's family is killed in a battle with the creatures. They set out for a nearby town where they manage to form a posse and hunt for the creatures. In the following days, they discover that the creatures are ancient and have lived near an Indian tribe that may be able to shed more light on these ghastly invaders. Mark and Jane Markham fall in love and agree to help each other in solving the mystery and answering numerous questions about the violent creatures that terrifies them.