Zerah Colburn was a well-known nineteenth century locomotive engineer, journalist and publisher.In life he mixed with the famous men of engineering in America and Britain. Ans he was among 200 leading Americans nominated for New York University's Hall of Fame.But Colburn was an enigma, a dark and irascible man with a violent temper. His work colleagues in London called him the 'Spirit of Darkness'. But why did he shoot himself at the age of 38 at the height of his career?