Charlie's parents have left him (again). This time they are off to South Africa to help giant golden moles. And Charlie? He's been dumped with his TV-obsessed grandparents. Lonely and curious, Charlie heads to the village of Castle-on-the-Hudson, where a frightened old woman gives him a desperate message-in sign language. When the woman suddenly disappears, Charlie is determined to find answers. Frog, who is Deaf, would rather be solving crimes than...