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.

A dangerous rogue dominant who Sloan thought was dead returns seeking revenge. The scientists discover even more advanced dominant biotechnology.

With a new serum, Dr. Tate hopes to convert dominant DNA into that of humans. With his new procedure, Tate alters monkey's DNA to dominant DNA, then injects it with the compound to return it to normal. When the animal appears to suffer no ill effects, Daniels volunteers to be a test subject as well. If Daniels is not killed by the drug, it could save millions of lives.