Matt is an ordinary teenager too young to remember the Great Drowning, the climate catastrophe that transformed England into a superheated archipelago. On a secret island he stumbles across a laboratory full of half-human and half-animal teenagers. When the shadowy Sons of Noah arrive to wipe out these hybrids, Matt is compelled to help three of them make a daring escape. Now they face a desperate journey through crocodile-infested creeks to save their captured friends. But a teenage cyborg assassin is on their heels with orders to kill. And worse dangers block their path, everything from ravenous kid cannibals to the zombie-like 'mushies'. Slowly, Matt realises that humanity's future depends upon their mission.