When Dr. Tom Greenbaum faces that question after successfully discovering the secret to time travel, he knows the time, place and event he will witness: the death and failed resurrection of Jesus Christ. Dr. David Goodman, Tom's colleague and closest friend follows Tom into the past, attempting to avert a time-space catastrophe, but forces beyond their control toss them into a dangerous end game where they are tempted by evil characters, betrayed by friends, pursued by an assassin from the future and haunted by a demon that cannot be killed.