Day One tells the story of life on earth following a global catastrophe that has devastated the world's infrastructures. Beginning with the immediate aftermath of the cataclysmic event, an eclectic band of survivors - strives to rebuild society as they unravel the mysteries of what happened and face their uncertain future. The group, all residents of one apartment building in suburban Van Nuys, Calif., embarks on a quest for survival and discovers that hope is found in small victories -- and heroes are born every day.