This book chronicles the apparent discovery of "memory molecules" in 1965, the loss of credibility that plagued those finding, and the subsequent triumphant discovery of the neuroactive peptides, including endorphins, which followed in their wake. The story is told in the context of the historical development of neuroscience as a field, with emphasis on research aimed at uncovering the brain mechanisms of learning and memory, roughly from 1950 to 1980, when the revolution in the scientific study of brain function was getting underway. A series of biographical vignettes paint the background and set the stage. Once introduced, the characters recur as their personal histories intertwine with the scientific story that unfolds. This seminal episode in the history of neuroscience flows smoothly for the lay reader as an engaging story of the clash between personalities, conventional wisdom, and unconventional explanations, supplemented by an essay with extensive documentation for the historian interested in this curious episode in the early years of neuroscience.