Mrs. Malaprop again presents Jack to Lydia, but this time with Sir Anthony present, exposing Jack's pose as "Beverley". Lydia is enraged by the puncturing of her romantic dreams, and spurns Jack contemptuously.
Sir Lucius has also learned of the proposed marriage of Jack and Lydia, and determines to challenge Jack. He meets Jack, who, smarting from Lydia's rejection, agrees to fight him without even knowing the reason. They will meet at the same time as Acres is scheduled to fight "Beverley".
At the duelling ground, Acres is very reluctant to fight, but Sir Lucius will have no shirking. Jack and Faulkland arrive. Acres learns that "Beverley" is actually his friend Jack, and begs off from their duel. However, Jack is quite willing to fight Sir Lucius, and they cross swords.