In 1927, Swedish traveler Astrée Sternhjelm, Zarah Leander and her elderly aunt Ana Sternhjelm, Julia Serda, are nearing the end of a sunlit visit to Puerto Rico. Ana despises the island and views it as backwards, while Astrée falls under its warm Caribbean climate, the openness of its people, and the infectious rhythm of habanera music. On their last day, they encounter Don Pedro de Avila, a powerful landowner whose wealth and charm captivate Astrée. He invites them to a bullfight, where he heroically leaps into the ring after the matador is injured and himself kills the bull. The next day, as their ship prepares to sail back to Sweden, Astrée makes a spontaneous decision to stay. She races down the gangway to find Don Pedro waiting, and before long they are married, sealing a dramatic new chapter in her life.
Ten years pass, and in 1937 a scene shifts to Stockholm. Dr. Sven Nagel, Karl Martell and his associate, Dr. Gomez, Boris Alekin, bid farewell to Ana, who asks them to return with Astrée for the sake of the Swedish family and to investigate a strange Puerto Rico fever. Ana’s foundation sponsors the mission, and she also asks the doctors to bring Astrée back to Sweden. In Puerto Rico, however, Astrée remains trapped in a loveless, stifling marriage to Don Pedro; her paradise has turned into a prison, and her son Juan is her sole reason to endure. Don Pedro makes no secret of his plan to seize the boy if Astrée attempts to leave.
The doctors arrive and quickly realize that their presence unsettles Don Pedro and his associates, who fear the fever’s discovery could devastate their business. An earlier attempt by researchers from the Rockefeller Institute to find a cure had failed, leaving the illness shrouded in mystery and triggering a severe economic downturn for the island. Hundreds die each year, but those responsible for the disease’s concealment keep it hidden and suppress any outside inquiry. The doctors proceed with their investigation in secret, conducting lab work in a hotel room to avoid local interference, a clandestine effort that underscores the peril they face.
Meanwhile, Astrée and Don Pedro clash over Juan’s upbringing. Don Pedro wants the boy trained for bullfighting, while Astrée has been teaching him about snow, Sweden, and the world beyond the island. The conflict intensifies, and Astrée secretly plans to escape with Juan by boarding the next ship bound for Sweden. Yet the departure is not for twelve days, leaving her in a tense limbo as the fever takes its toll on the island’s inhabitants and the doctors press on with their work.
Don Pedro soon suspects that Astrée’s old lover Dr. Nagel is involved in her plans. He arranges a grand party at his mansion, hoping the social gathering will provide an opportunity to search the doctors’ hotel room and gather incriminating evidence that could lead to their arrest and deportation. At the party, Dr. Nagel and Astrée reconnect; a former love re awakens, and Astrée’s voice rises with La Habanera, a performance that doubles as a confession of her lingering feelings for Nagel. Don Pedro’s suspicions intensify when he learns that the hotel-room raid has yielded enough evidence to move against Dr. Nagel, threatening to derail the doctors’ mission and jeopardize Astrée’s fragile hope of escape.
Just as the doctors stand on the brink of arrest, Don Pedro collapses, drenched in sweat. Dr. Nagel diagnoses Puerto Rico fever and calls for a newly developed antidote from his hotel-room supplies, only to discover that Don Pedro has deliberately destroyed all medical materials—antidote included—during the raid. The moment is chaotic, and Nagel privately condemns Don Pedro, declaring that the tyrant has “dug his own grave” as the man dies.
With the power base of his mansion dissolved, Don Pedro’s estate is donated to the poor to serve as a retirement home. Astrée, now a widow, is free to pursue her future: she can return to Sweden with her lover and her son, leaving behind a life that once seemed a paradise but proved to be a trap.
In the end, the film leaves viewers with a sobering portrait of love constrained by wealth and control, the stubborn resilience of a woman seeking autonomy, and a clandestine medical quest fighting against a cover-up that imperils an entire community.
