Nancy becomes involved in another mystery when she accepts an invitation from Mrs. Chantrey, a client of Mr. Drew, to vacation at her cottage in a picturesque seaside town. Carson Drew has promised to join his daughter, but fails to arrive. The alarming disappearance of Mr. Drew and the odd circumstances surrounding his rescue are only the start of a series of highly dangerous adventures for Nancy and her friends Bess and George. Mrs. Chantrey's story about a nearby Cliffside cave reputedly inhabited by a ghost intrigues Nancy and she decides to investigate. Several frightened townspeople claim to have seen an apparition and heard the weird sounds of a tolling bell just before water rushes from the cave. Will Nancy discover the true cause of these mysterious occurences?