The Day the Stones Walked By T.A. Barron Illustrations by William Low Philomel Books: 32 pp., color illustrations, for ages 9 to 12, $16.99 Pico is embarrassed by his father. Unlike other fathers on Easter Island, who might teach their sons how to build a boat or hunt octopus, his "Pala" is obsessed by the great stone statues that look out over the ocean. The origin of these moai is a mystery, but -- how humiliating -- Pala thinks they can move, that they are the ancestors and protectors of the people. Pico changes his mind about them on the day of the Great Wave (we'd call it a tsunami). Half-drowned, he hears "the sound of great feet. . . . And voices, deeper than the sea itself." Could it be that the stones walked? Well, that would explain a few things. Barron's dramatic text is matched by Low's careful use of light and shadow in his compelling illustrations. Although the publisher targets the book for ages 9 to 12, younger readers could handle the scary parts if guided by a trusted adult through the flood sequence.