This document provides an introduction to Leon Denis' book "The Mystery of Joan of Arc". It argues that to truly understand Joan of Arc, one must study psychic science, as her extraordinary life and achievements can be explained by invisible psychic forces. It discusses how Joan has been both exalted and attacked by different groups. The introduction aims to find the truth between the extremes by examining Joan's story through the lens of psychic phenomena, which were just beginning to be studied scientifically in the late 19th/early 20th century.