After the world's population has been ravaged by a pandemic, a man lives a lonesome existence in a Colorado airplane hangar with his dog and a dour gunman he has befriended. When a mysterious transmission comes through on the radio while he’s flying his old Cessna, it sparks a hunt for the provenance of the sound.

Twenty-eight days after a killer virus was accidentally unleashed from a British research facility, a small group of London survivors are caught in a desperate struggle to protect themselves from the infected. Carried by animals and humans, the virus turns those it infects into homicidal maniacs -- and it's absolutely impossible to contain.

As London is submerged below floodwaters, a woman gives birth to her first child. Days later, she and her baby are forced to leave their home in search of safety. They head north through a newly dangerous country seeking refuge from place to place.