The Mystery of the Coughing Dragon — Nick West

Henry Allen's dog is missing. He thinks it's been eaten by a dragon! He swears he saw a dragon emerge from the ocean and slither into the caves underneath his cliff-top house.

The Three Investigators don't know if they believe Mr. Allen, but they're determined to find the dog. And that means exploring those dangerous caves…where something evil lurks, ready to catch unwary pets -- and detectives!