A deadly virus has spread across the globe. Contagion is everywhere, no one is safe, and no one can be trusted. Four friends race through the back roads of the American West on their way to a secluded utopian beach in the Gulf of Mexico where they could peacefully wait out the pandemic. Their plans take a grim turn when their car breaks down on an isolated road starting a chain of events that will seal their fates.

After failing to apprehend the terrorist behind a Paris attack that claimed dozens of lives, CIA agent Alice Racine is forced to live in London as a caseworker. Her mentor unexpectedly calls her back into action when the CIA discovers that another attack is imminent. Alice soon learns that the classified information she's uncovered has been compromised. Running for her life, she turns to a former soldier to help her prevent a lethal biological attack on the citizens of London.

An alien microbe lands in remote Siberia in the 1950's. In the year 2004, US scientist working at a top secret underground lab in Alaska clone the microbe. A garbled distress signal is heard from the lab just before a complete lock down of the facility. This is the last word sent out from the scientists. A team of scientists and military personnel are in charge of finding out what went wrong.

In a world ravaged by a virus infection, turning its victims into the Undead, Alice continues on her journey to find survivors and lead them to safety. Her deadly battle with the Umbrella Corporation reaches new heights, but Alice gets some unexpected help from an old friend. A new lead that promises a safe haven from the Undead takes them to Los Angeles, but when they arrive the city is overrun by thousands of Undead - and Alice and her comrades are about to step into a deadly trap.