Dr. Cal Lightman is the world's leading deception expert. He studies facial expressions and involuntary body language to discover if and why someone is lying. He partners with a clinical psychologist, and opens up an agency that assists law enforcement, government agencies, and private individuals when they hit roadblocks in their searches for the truth. One of their first cases involves the son of a family of devout Jehovah's Witnesses. He is accused of killing his teacher after being caught fleeing the scene of her murder.