The Forest of Dean anomaly reopens, and people start vanishing at an alarming rate. Helen turns up and says they're being invaded by a creature unlike anything the world has ever seen - a highly evolved predatory bat from the future. Things get worse when they discover a brood of infants. After killing the parent, Helen and Nick agree to take the young through the Permian anomaly, to find the gateway to the future and stop any more from coming through. But their forays into the past could have catastrophic consequences.