Franklin Endicott and the third key

"Frank Endicott is a worrier. He worries about lions, submarines, black holes, leprosy, and armadillos. He lists his worries alphabetically in a notebook and suffers vivid nightmares that even a certain neighborhood pig can't dispatch. When he accompanies Eugenia Lincoln on an errand to duplicate a key at her favorite dark and dusty thrift shop, Frank earns fresh cause for alarm. Odd Buddy Lamp, the shop's proprietor, has sent them home with the...