The Shiftling plot
When Allen Monroe, a reporter for an adventure magazine, goes in search of his missing friend, he finds that he has become the target of an indestructible creature known as the 'shiftling'. Immortal, and able to invade and control humans, the shiftling is aware that Allen is the last on Earth to know of his weakness; a relic left behind that is capable of subjugating others. Allen sets out in search of the relic, as does a technologically gifted billionaire who believes he can amass immortality by capturing and studying the shiftling. The perilous quest for the relic pits two people against each other, while the 'shiftling systematically hunts them.