In the late nineteenth century, visitors to Maine observed something strange: French-Canadian lumberjacks who, at the slightest stimulus, seemed to jump, strike out with their limbs, or mimic languages they could not speak. Ross Bullen introduces us to these so-called “Jumping Frenchmen” and to their greatest investigator, George M. Beard, who saw a link in their behavior between religious frenzy and neurasthenia.