The Well of the King

From the introduction: The Heroes are in a village when they hear a disturbance near an outlying well. The villagers are yelling that little Timmy was playing near the well when several small people came out and grabbed him. His pet collie attempted to fight them off and they shot it with a little arrow. They are afraid to go into the well after Timmy. Timmy’s poor mother begs and beseeches the Heroes to go after him and rescue him.