After the suspicious death of her mentor, Dr. Ann Coulter, bio-anthropologist Dr. Sloan Parker continues their study of a serial killer's DNA and, together with Dr. Ed Tate, discovers a new humanoid species that could replace humans.

Sloan searches for more of the new humans, only to find more puzzles. But she may have found an ally in Tom Daniels-which she needs after Lynch escapes.

Lynch continues his killing spree as Sloan and Ray pursue him; and Sloan and Ed may have a clue to the geographical origin of the new species.

Sloan, Tom and Ed travel to Mexico to search for clues about the origin of the new species, where they make a discovery that may reveal how many of the new humans exist. When they return, Tom investigates his own origins by visiting his boyhood home.

Attwood brings the pillar from the secret city back to the United States so that Sloan, Ed and Tom can investigate its meaning. With its arrival come new dangers for all of them.

The bombing of a bar, intended to kill a reporter, leads Tom and Sloan to Tom's old mentor, a cold and ruthless man who trains the new species for violent missions.