One day, a resolutely ordinary young man named Mr. Whatwilltheysay returns home to find Grain-of-Sand, a mermaid, waiting for him in his favorite armchair. Despite his objections, the two embark on a series of very watery adventures as he tries to get rid of her. But ultimately the thought of being seen with half a fish is simply too much for Mr. Whatwilltheysay to bear—what would people say? So broken-hearted Grain-of-Sand returns to the sea in his bathtub, leaving Mr. Whatwilltheysay to resume his pedestrian existence. Mr. Whatwilltheysay soon finds that his beloved landlubber life, however, lacks the splash and shimmer (and bathtub) of his good times with Grain-of-Sand—and acting against all his instincts, he sets off to sea to find her.