Five years ago, a toxic microplastics storm killed most of the population. Now Katie, a young mother, must forage and hunt the few surviving animals for meat as she attempts to feed her little boy, Harry. At a time when stepping outside could kill you, Harry is kept indoors at all costs, never venturing beyond the door to their one-bedroom flat.

Bodies begin to build up around them and layers of poisonous dust hang heavily in the air, seeping into the soil and slowly killing anything attempting to cling onto the natural world. Then, after years without human contact, Katie and Harry are terrified by the unwelcome arrival of another survivor. Katie realises she must undertake a previously unthinkable journey in search of the man she was supposed to marry and a new life for her son. But outside their safe haven, Katie and Harry encounter a dangerous world that is forever changed.