Reeling after the attack on their block of flats, the survivors assess the damage and prepare as best they can for the winter to come. Food, medicine, water and soon power will be gone. Jack, determined to save his friends and neighbours, leads a group out into the city in search of supplies. Sarah, faced with the hard choice of watching people die without their medicine, makes a decision of her own.
As a storm gathers over the city, the survivors face danger unlike they have ever known before as the weather turns against them, the infected stalk the shadows and even the cities vermin have developed a taste for human flesh.