At the Center for Disease Control, epidemiologist Dr. Kayla Martin (Tiffani Thiessen) and her partner Carl Ratner (French Stewart) receive a frantic call from a flight attendant high above the Pacific. A nineteen-year-old male passenger, en route to Los Angeles from Australia, has died following a raging fever and violent convulsions. Vehemently concerned about the symptoms, Kayla orders all passengers quarantined upon their arrival at LAX a decision at odds with Mayor Richard Delasandro (Eric Roberts) who suggests the only outbreak will be one of panic. The CDC considers the frightening possibilities the reality of the flu, the probability of a biological attack, or worse, a new virus they can't control. By the time the passengers of Flight 182 are filtered into the ward of a local hospital, the infection is already poisoning sections of the city, unbeknownst to each victim who passes it on. While Ratner and FBI Agent Troy Whitlock (Vincent Spano) work with Australian officials to find the source of the virus now dubbed "Riptide," a media manipulation of the human interest angle fires up an ACLU attorney who exploits the "unlawful quarantine' to satisfy her own divisive political agenda. Only Kayla and her team know the unavoidable facts. The virus is spreading, and so is the panic and the fear that it can't be stopped. From a Los Angeles morgue to a foul, death-ridden apartment complex in Australia to a beach shack in El Salvador, the hunt is on for Patient Zero. Time is running out.