The summer before entering sixth grade, Sammy, a bright and charming boy who lived on the coast of Maine, suddenly began to exhibit disturbing behavior. He walked and ate with his eyes shut, refused to bathe, burst into fits of rage, slithered against walls, and used his limbs instead of his hands to touch light switches, doorknobs, and faucets. Sammy's mother, Beth, already coping with the overwhelming responsibility of raising three sons alone,...