When her husband is attacked by a zombified neighbor, Ana (Sarah Polley) manages to escape, only to realize her entire Milwaukee neighborhood has been overrun by the walking dead. After being questioned by cautious policeman Kenneth (Ving Rhames), Ana joins him and a small group that gravitates to the local shopping mall as a bastion of safety. Once they convince suspicious security guards that they are not contaminated, the group bands together to fight the undead hordes.