The late 19th century was the golden age of scientific quackery, and the American West was its motherlode. Daniel Spurlock, a mentally troubled Texas orphan, turns to phrenology for clues to his brain's mysteries. His phrenological skill leads to a lucrative practice, and his discovery of the "murder organ" - the part of the human brain that instills both a predilection and a talent for homicide - brings him to the forefront of the emerging field of forensic science. But an ill-considered marriage proposal to his invaluable assistant, a disastrous pilgrimage to the Italian castle of a reckless brain surgeon, and phrenology's waning popularity shatter his carefully nurtured equilibrium and reduce him to private detective work. Called to Chicago to assist in a sensational murder trial, Spurlock comes face to face with the limits of science and reason, and the hard truths of fickle love and frontier justice.