Retired virginal botanist Félix Cotnoir falls madly in love with Helena Mentana after seeing her dressed as a mermaid on the cover of her novel Kalamazoo. The commercial failure of this novel drives her to take refuge in Saint-Pierre and Miquelon Islands, where Félix intends to track her down. He memorizes the novel and is whisked away in an intoxicating romance with the mermaid of his dreams until it vanishes into the waves and he finally meets the real Helena Mentana.