Don't Walk Alone (Windswept Mystery/Romance #1)1982

Danny led me along a small path that ran parallel to the sea. There was plenty of space between us and the edge of the cliff, but the sea was far beneath us I grew dizzy with fear. “Promise me one thing,” Danny said. “DON'T EVER WALK HERE ALONE.” Amy's first feeling when she sees Crozier's Cottage, her new home, is fear. The “cottage” is actually an isolated old house perched on ragged cliffs with the ocean crashing below. But life seems brighter when she starts dating Danny Morgan. Then suddenly Danny breaks off with Amy -- and won't tell her why. Only then does Amy wonder about the three strange men she'd seen lurking on the cliffs, the look of fear in Mrs. Morgan's eyes, and Danny's mysterious coldness. The terror begins again. Something is wrong -- and Amy knows the sea hides the answer.