Leon and his younger sister, Grace, have recently moved to London from New York and are struggling to settle into their new school when rumours of an unidentified virus in Africa begin to fill the news. Within a week the virus hits London. The siblings witness people turning to liquid before their eyes, and they run for their lives. A month after touching Earth's atmosphere the virus has assimilated the world's biomass. But the virus isn't their only enemy, and survival is just the first step.