What is this strange man's secret, and why does he seem so familiar?

Delirious and feverish, at a place called Valley Forge, Head of Stone stumbles into the arms of Martha Dawson who is the spinster of Phillip and Elizabeth McCray. Because Elizabeth has an infant son, Robert, Phillip and Martha decide it is best to keep Elizabeth away from this man. However, somehow, this young man seems strangely familiar. Who was he and why is he, an obvious white man, dressed as a Native American? 

Head of Stone had been living with the Lenape in Western Pennsylvania since he was captured as a child and sold to the tribe. He had raised by them and had married one of them and they had a son together. However, she had been ruthlessly murdered by white men and Head of Stone had been following them to seek his revenge for murdering the mother of his child. This stop at this cabin at Valley Forge, however, was going to change his direction and the course of history for a ragtag army on what appeared to be its last legs.