The gentle conquistadors are Cabeza de Vaca and his party--Spanish captains Dorantes and Castillo, and the slave Esteban--who, separated from the ill-fated Narvaez expedition near the mouth of the Mississippi, spent a six-year ""apprenticeship"" among primitive Gulf Coast Indians before escaping to make their way westward to Spanish suzerainty in Mexico. This epic journey figures largely in the biographies of Vaca by Syme (First Man to Cross America) and Wojciechowska (Odyssey of Courage); but its projection of its singularity--the Europeans and the black Christian enacting successively the roles of Healers, guardian spirits and Children of the Sun expected of them by mythologizing Indians--gives Jeannette Mirsky's novel a different cast. And because she is hypothesizing, a very different opening and conclusion, both aggrandizing Esteban, about whom little is known beyond Vaca's testimony to his character. All this she explains in the Author's Note at the close, which adults should perhaps read before passing judgment on her liberties. For although the start is slowed by circuitous conversation, the Indianization of the four quite fills the fictional framework. Not sinews-and-grit survival but presumably the title will pre-select the reader.