In 19th-century New Zealand, two sisters compete for the same man against a backdrop of political unrest and natural disaster.

In the 1840s, after a lengthy absence, Dr. Edmond Ozanne, a widower, and his handsome young son William return to their home on Green Dolphin Street on the English Channel island of St. Pierre. Their arrival causes a stir at a nearby convent and prompts the worried Mother Superior to rush to the home of Sophie Patourel, Edmond's former sweetheart, with the news of their arrival. Sophie, now married to the dull Octavius Patourel, was once madly in love with Edmond, but his drinking and her parents put an end to their romance. Sophie's two daughters, the shy Marguerite and the outgoing Marianne, both fall instantly in love with William and pay a friendly visit to the Ozannes. Later, while strolling through the town market, Marguerite receives a bouquet of flowers from her secret admirer, Timothy Haslam. After killing a man in a knife fight, Timothy takes refuge aboard the New Zealand-bound clipper Green Dolphin . Although the captain of the ship, Captain O'Hara, discovers Timothy before the ship leaves port, he allows the stowaway to sail with him because he is undermanned. Back on St. Pierre, William tells Marianne that he dreams of sailing the world, and she, hoping to win his favor, arranges to have him enlisted in the Navy. Years pass, and William, home on a furlough, professes his love not for Marianne, but for Marguerite, who responds in kind. Later, while docked in a port town in China, William misses his ship and inadvertently becomes a deserter when a shopgirl drugs and robs him. After regaining consciousness, William stows away on the Green Dolphin and disembarks in New Zealand, where he befriends Timothy. While settling in New Zealand, William writes Octavius for permission to marry Marguerite, but he accidentally writes Marianne's name in the request instead. Upon learning of this, Timothy insists that William shield Marianne from the truth and that he marry her out of pity. Meanwhile, Marguerite has become despondent following the death of her parents and has joined the convent seeking comfort and direction. Years later, Marianne and William have settled in New Zealand. Tragedy strikes, however, when a massive earthquake destroys the New Zealand town where they have settled, and Marianne nearly loses William and her unborn daughter. Several more years pass, and Marianne, William and their daughter Veronica are forced to leave their home when the region becomes a battlefield in the civil war between the Maoris and the colonists. William, Marianne and Veronica eventually return to St. Pierre after Marianne has her husband officially absolved by the Navy for his desertion. Soon after they arrive on St. Pierre, however, Marianne discovers a letter proving that William really intended to marry Marguerite. Marianne confronts William with the truth, and although he admits to the deception, he insists that he now loves Marianne. Marianne is hurt by the truth and tells Marguerite about William's blunder. When Marguerite assures Marianne that she has forgiven William and has found true happiness in her religious pursuits, Marianne puts aside her anger and vows to repair her marriage.