The battle has just begun. To save the future, Anthony Reynolds and Sephora Ashton must change the past by becoming cold-blooded assassins. The interdimensional entities have established a tetrarchy spanning four epochs of Earth, thousands of years apart. Anthony and Sephora will have to travel back through time in order to eliminate each tetrarch—hiding inside the skulls of unwitting human hosts—in order to destroy their foothold in our reality. Otherwise, the interdimensionals will absorb all that we have and leave us with nothing. To accomplish their mission, Anthony and Sephora must rely on each other and trust Peter Gideon, a young man brought back from the dead who cannot leave the space-between-space without reverting to a mindless zombie. Traveling aboard his ethereal aeroship, existing outside of time, they will track down each of the tetrarchs' interdimensional signatures. But it won't be smooth sailing. The Moule people, possessed by the Red Queen's acolytes, are hunting them, determined to derail their efforts at every port. And Anthony, overwhelmed by doubts when he discovers who his parents were in the real world, may end up jeopardizing everything he and his friends have fought for.