Professor Paul McCracken's final message to parasitologist Dr. Sara Devlin is brutal, but clear: he'd rather die than let the alien parasite within him live. For Devlin, the shock of McCracken's suicide is quickly replaced by the horror it reveals—the existence of a microscopic extraterrestrial organism with the ability to infect and control its human hosts. McCracken wasn't the first person to be infected. There are others. Many others, extending back to the dawn of mankind.

At first, Devlin believes the authorities are slow to recognize the alien threat and respond to it. But the truth is far worse—rather than stop the parasite, there are those seeking to replicate it, control it...and even weaponize it. Working with McCracken's research and a fractured network of allies, Devlin must outmaneuver secret government organizations, foreign military agencies, and the growing legion of infected hosts to thwart an extraterrestrial invasion thousands of years in the making.

Scientists spent decades scanning the universe for signs of alien life, but they should have been searching closer to home...