The story centers on the redemption of its lead female character. George Brent is Tom Ransome, an artist who leads a rather dissolute if socially active life in the town of Ranchipur. His routine is shattered with the arrival of his former lover, Lady Edwina Esketh (Myrna Loy) who has since married the elderly Lord Esketh (Nigel Bruce). Lady Edwina first sets out to seduce, then gradually falls in love with, Major Rama Safti (Tyrone Power) who represents the "new India."
On a beach in Australia, two American surfers say goodbye to each other as one is about to leave for his flight back to California. The two men don't notice the large number of dead birds on the beach. On the flight, the surfer returning home starts coughing up blood and dies before the plane can land. Back in Australia, the other surfer is found dead in his apartment. Kayla Martin (Tiffani Thiessen) is a medical doctor with the Centers for Disease Control and Prevention (CDC) who has been assigned to the case. She and the local officials carry the body of the surfer out of the plane and start processing people to be put in quarantine until they can be evaluated for exposure. During the transfer, one of the passengers escapes to complete a business deal and unknowingly spreads the virus throughout Los Angeles. It is also revealed that outbreaks of the so-called "riptide virus" (as it comes to be known), an offshoot of the bird flu, are occurring in other cities around the world.