A storm from hell itself? After a weekend stopover in the big city, the six passengers of a double-decker bus are on their way home at night. Maddie, their driver, is tough and experienced... but soon very out of her depth. Before they can reach the outskirts of the city, a rainstorm begins like no other Maddie has ever encountered... This rain is raw, searing acid. Just a drop on human skin is enough to inflict an agonising burn...