A 1932 Washington, D.C., demonstration by WW I vets hoping to collect a promised bonus is the basis for a novel about how nine-year-old Jimmy Watkins joins his unemployed father in the effort. At first, it's an adventure and escape from growing responsibilities; but as Jimmy settles into the hobo camp where the marchers await President Hoover's decision, he becomes aware of the hunger and hopelessness around him and is moved to acts of kindness. When Congress votes to defer the bonus until 1945 (why isn't explained), the squatters are routed and Camp Marks is burned by troops. In a dramatic but unrealistic scene, Jimmy calms the panicky crowd and leads it, Pied Piper-style, out of the camp by playing his harmonica. Though pedantically written, the story is packed with authentic details extended in an afterword describing Roosevelt's different response to the next bonus march. Ethereal watercolors elevate the text but reinforce the romanticized presentation rather than depicting the time's true squalor. Nevertheless, a serviceable addition. (Fiction. 8- 10)