Passing through a portal in the time/space continuum, a man finds himself in the sixteenth century defending a tribe of hunter gatherers in the great southwest who are on the brink of extinction.  A young girl with a birth deformity was declared to be a curse.  The superstitions of the tribe required that she be cast out to die of exposure, starvation or under the fangs and claws of some beast, but she survived. 

The man gathers a group of young people who were willing to fight for survival. With this group the young "curse of the tribe" finds her family. (Book One)

As the tribe emerges into self sufficiency, so does the demand that the "Curse" must be destroyed. After a deliberate and determined attempt on her life is barely thwarted, they embark on an "Incredible Journey" to find a cure. (Book Two)

The influx of fleeing bands of displaced and destroyed tribes was posing a hazard and burden on the little tribe trying to get back to self sufficiency and self respect. With little food and meager resources, they were constantly on the verge of extinction.

Now a new threat had entered the valley. With the Aztecs, Mayans and Incas destroyed and their gold confiscated, the conquistadors had turned their eyes north. Gold had been found in several little rivers and streams coming out of the mountains and the great river and huge valley would undoubtedly lead to more.

The native population had no weapons that could penetrate armor and no one could out run the great beasts ridden by the conquistadors. Furthermore, the powerful thunder sticks that rolled out smoke and death, prevented any warrior from getting close enough to attack their army.
How can they survive the coming destruction? (Book Three)