The story is set in autumn 1937; with strong objection from the Imperial Army, Lieutenant Colonel Yuki establishes the D-Agency, which trains spies for insertion into other countries. General headquarters' colonel Muto nominates first lieutenant Sakuma to monitor the D-Agency, and orders the agency to investigate John Gordon, who is suspected to be an American spy. Disguised as military police, the training spies and Sakuma search the home of Gordon for evidence proving that he is in fact a spy. Sakuma's life is used as a pawn by one of the other spies when the his committing seppuku is used as a bargaining tool to get inside of Gordon's home. However, it seems clear that actually Sakuma is being played by his superior and the other spies and there is no evidence linking Gordon to being a spy.