Astrée Sternhjelm is visiting Puerto Rico with her aunt Ana, and is enchanted by the island. The day before leaving she meets the wealthy Don Pedro at a bullfight arena, and is infatuated by him. Just before the ship takes off, she hears the song “La Habanera” sung by some natives at the quay. The song strikes a chord in her heart, and without hesitating she leaves the boat to find Don Pedro. After some weeks they get married. Ten years later her paradise has turned into hell. She is locked up with her son Juan in the big estate by her jealous and controlling husband. In Stockholm her aunt Ana is financing a foundation, which is sending two doctors to Puerto Rico to research a tropical fever. One of them, Dr. Sven Nagel, was once in love with Astrée, and the aunt asks him to find out what has happened to her niece. When the two doctors arrive to the island, they are met with hostility from the authorities and the local doctors, who are afraid that news about the tropical fever in the world press, would cause all investors to withdraw from Puerto Rico. The Swedish doctors succeed secretly to get a bacteriological sample and develop an antidote. Don Pedro invites them to a party in his house, as part of a plot to get them imprisoned.