Nathan K -- he can hold two souls in his body. If he dies, he loses one yet lives on with the other. As long as he replenishes his second soul, he cannot be killed. Nathan K is immortal.
ON THE HUNT
Nathan, Robin, and Altman have been after any lead to find Russo, the Immortal responsible for hospitalizing Altman's sister. They've traveled throughout Europe, always one step behind an elusive assassin making sure they never get what they seek. But when they discover key information before the assassin, they are set on a race to retrieve a laptop holding enough secrets to expose Russo forever. But it will also put all Immortals at risk.