The mysterious man known as Dr. Armgaard Karl Graves was a double agent working for the German secret service and MI5 before the start of the first world war.

In 1912 he was arrested in Scotland and imprisoned. But after 8 months he was mysteriously released and shortly afterwards appeared in New York, where he caused a sensation by publishing his memoirs of his service as a spy, which sold over 100,000 copies. His reminiscences are a fascinating insight into espionage in Europe at the end of the 19th century.