Ernie is a troubled thirteen-year-old juvenile delinquent. Abandoned on the doorstep of an orphange when he was three years old, his only proof that he once belonged to somebody is a vintage Ernie Banks baseball card, a crystal acorn he wears on a string around his neck, and a strange spiral birthmark on the bottom of his foot. As a last reprieve before being sent to a juvenile detention facility, Ernie is allowed to spend three weeks on a working farm. When Ernie learns that the farmer's baby was kidnapped years before, he is determined to solve the case. Teaming up with Joey, a local tomboy, they investigate clues that lead them on a dangerous journey into a forbidden world of dark secrets, magic puddles, and the cavernous undergroun kingdom of the Puddlejumpers--eleven-inch-tall water creatures with whom Ernie has a mysterious connection.