The Ghost of Craven Cove — Carolyn Keene

MYSTERY IN THE MISTS....
Nancy, Bess, and George have been invited by their former grade-school teacher June Braden to spend their vacation on the coast of Maine. Miss Braden's brother, Karl, was recently lost at sea and is presumed dead, but his daughter swears she has seen him lurking in the caves of nearby Craven Cove. Nancy vows to help Laura Braden determine the truth about her father's fate, once and for all.

The waters off Craven Cove are treacherous and rocky, and so too are the stories swirling around the case of Karl Braden. Ignoring a series of threats warning her to mind her own business, Nancy discovers that there's more to THE GHOST OF CRAVEN COVE than meets the eye. For when a dead man walks, danger is sure to follow in his footsteps.