 Through his network of spies, Chauvelin discovers that Armand St. Just, Marguerite's brother is one of the Scarlet Pimpernel's agents.Chauvelin orders Armand's arrest, then uses the threat of his execution to force Marguerite into helping him discover the identity of the Pimpernel, who he knows will be at an upcoming ball.At the ball, Marguerite intercepts a message given to Sir Andrew Ffoulkes, a member of the Pimpernel's band, stating that the Pimpernel will be in the library at midnight.