Marred somewhat by its rather close resemblance to James Vance Marshall's gentler Walkabout (1961), this is an effective ordeal of growing-up-in-the-wild--beginning when 13-year-old Sarah Francis accompanies her father on an expedition into the upper Amazon where he is conducting an archaeological dig to uncover a pre-Incan civilization. The dig is a terrific success, but the other members of the team are struck down by a disease, leaving Sarah and her father to care for the site. And then, when her father is killed by a falling stone in an underground doorway, Sarah feels impelled to try to get back to civilization by way of the Itui fiver. After four days or so, she knows she's lost and falls in with a young native, Juma, learns his language, spends an idyllic time with him absorbing jungle lore, then follows him to his village. But her welcome is cut short when she takes out a magnifying glass and starts a fire, an act they consider fearful magic. And when Sarah is exposed to certain strange burial and dietary practices, she flees down-river by a canoe and is later taken in by another tribe. . . of warlike headshrinkers. Again Sarah runs away in disgust and after a few weeks drifts by canoe into civilization. Her physical maturation is described frankly, and the army ants, fights between boa constrictors and trots, food and survival lore are made steamily graphic. A trifle oversensationalized, perhaps--but veteran Eckert, sticking close to the flora and fauna he writes about best, has done better here than in other, more densely populated novels.