A mysterious device from the distant future sends Alister Bernhardt and Allison Taylor back to the past, where they appear before the ancient Roman Emperor, Constantine the Great. Mistaking the young couple as the Goddess Isis and the God Osiris, Constantine abandons his plan to promote the budding Christian religion as the official state religion of Rome. The intrepid time travelers, upon returning to the present, discover that they have inadvertently and irrevocably altered history.
Desperate to reintroduce Christianity to the world, Alister uses the power of the mysterious device to perform miracles and to propel himself to religious stardom. But in this new reality, his sister Amanda, gifted haruspex and devout follower of the Goddess Isis, views the reinstatement of Christianity as nothing less than the end of her world.
In an incident with the device, when she and the High Priestess of Isis attempt to discover its purpose and power, the contact leaves her in a coma, her brain irreparably damaged. Alister uses the device to repair her damaged mind. The mechanism not only repairs, but it also enhances her mind giving her control over the device itself. She must now use her newfound powers to defeat the evil machine and to fight for the continued existence of her world.