James T. Longfellow, professor of history and medieval literature at Harvard, finds the body of his friend, Professor Julius Davenport, in Davenport's office at Yale University. The police ignore how he died and who may be behind the murder, but everything seems to be connected with a mysterious book written in strange characters that the victim had finally managed to translate. Longfellow, moved by the desire to solve the murderer of his friend, embarks on an investigation that takes him to the Vatican Secret Archives, where the original book was found, and eventually merges into a conspiracy of planetary scale by means of which a powerful secret society of ancient existence tries to ensure the hegemony of a chimeric superior race of alleged alien descent. Along the way, the timid professor discovers love and risk, and ends up becoming the linchpin that enables Western secret services to uncover the conspiracy and defeat it. However, few things and few people are what they seem.