Atheist Ted Duncan finds himself face-to-face with a copy of himself from a parallel universe. The other shares with him a common history; his counterpart, however, is Christian. The pair are given controls to the Tuning Station, a machine that allows them to observe their pasts, and assigned a deceptively simple task: discover the exact moment their lives diverged.
As they delve into the mystery, Ted sees ghosts of his own childhood in his double -- an isolated kid suffering from Asperger's Syndrome, instilled with fear and insecurity by fundamentalist parents. Weaknesses he is certain linger from an unchallenged belief in a God that doesn't exist.
Revisiting his painful past only confirms for Ted that it was inevitable he'd leave faith and family behind. But his twin stands as a denial. What single event could have changed everything he knows to be true?