The team not only have to contend with a plague of mutated giant rats roaming the sewers of New York, but a trio of redneck hunters seeking to make Godzilla the ultimate hunting trophy.

When a strange electrical creature known as the Crackler attacks seemingly random locations in Manhattan, the team investigate. But the Crackler isn't behaving like the mutations H.E.A.T. have fought before, and what is its connection to mild-mannered insomniac Sidney Walker?

The team are called to help a rescue mission for xenobiologist Alexander Preloran, who disappeared while on a mission to explore the Leviathan, an alien spacecraft buried at the bottom of the Pacific for 65 million years. But once they go down, the team discover the ship's alien crew are very much alive... and they have plans for Earth.