During the festivities, Simplicius arrives with a bound captive, Melchior, whom he had discovered in the camp and arrested as an enemy. Before Melchior can be hanged he announces that he too is the Baron von Grübben, and as proof presents Wendelin's letter. The confusion is deepened when an imperial dispatch arrives from Vienna claiming that suspect papers and documents have been discovered in the residence of one Baron von Grübben. These papers are linked to Sweden, and orders are given to place the Baron under arrest until further notice. Melchior, who we know is in fact involved with the Swede Ebba, denies the allegations. Both Arnim and Melchior are placed under arrest, and Simplicius is made an ensign. The troops set out to fight the Swedes.