True Son’s Indian blood is metaphorical. His adoptive father conducted a ceremony to replace his White blood with Indian blood, to make him the “true son.”
True Son was captured from his White family by the Delaware Indian tribe when he was very young. As a result, he thinks of himself as an Indian. Apparently, his new family wanted to make it official.
More than once he had been told how, when he was four years old, his father had said words that took out his white blood and put Indian blood in its place. (ch 1, p. 4)
According to his father, his “white thoughts and meanness had been wiped away” in this ceremony, and an Indian’s brave thoughts replaced them.
Not only is this an example of how invested True Blood’s adoptive parents were in him, it is also an example of the indoctrination he underwent. True Blood was taught from the age of four that he was now an Indian, and he was strong while his former people were weak. This makes returning to them all the more difficult for True Blood.
True Blood is remembering this ceremony at a time when his father is returning him to his white family. He does not understand how he can be treated as a son for so long and then cast away, returned to a family he no longer knows.