Water purported to cure cancer puts Hood and Rachel searching for a scientific explanation, but the answer is more deadly than the diseases it's supposed to be curing.
Hood goes up against an FBI deputy director when a psychotic woman accuses the man of stealing her son, and the stakes go much higher when Rachel is taken hostage and Jacob is accused of complicity in the crime.
Hood is called in when people in Philadelphia begin falling victim to an unknown poison that affects the nervous system and causes one to become a fireball.
Dr. Jacob investigates an epidemic of violent outbursts by usually law-abiding citizens in a small Texas community but then exhibits to the same erratic behavior.
A case of mercury poisoning that could turn into an epidemic puts Hood, Young and an eager field agent to work tracing the source of the mercury, but as every lead becomes a dead end they must begin looking for an unnatural cause.
Gepetto resurfaces with the discovery of identical quadruplets from different mothers, leaving Hood and Rachel scrambling for clues to identify her, and the hit man she's hired, before another murder occurs.