The Parthenon represents, for many, a golden age in human achievement: the 5th-century b.c. Greek flowering of democracy, sciences, and the arts. But what if its chief ornament, the Parthenon frieze, turned out to be not an embodiment of reason and proportion—of stillness at the heart of motion, quiet piety, and enlightened civic responsibility—but (or, rather, also) something darker, more primitive: a representation of the critical moment in an ancient story of a king at war, a human sacrifice, and a goddess’s demand for virgin blood? That’s the argument at the heart of The Parthenon Engima. The plot involves not...