Unexplained anomalies are ripping holes in the fabric of time, allowing creatures from the very earliest stages of the earth's development to roam through the modern world. These creatures are ferocious, endearing and puzzling by turns but they all have the same simple fact in common - they don't belong here.
Their presence throws up a terrible dilemma - is history about to be turned on its head? Will humanity survive in the face of a new and unprecedented threat from other species? And most urgently of all - will you find a Velociraptor in your garden the next time you open the door?