De Flores takes Alonzo down a passage in the castle. De Flores and Alonzo both carry swords. De Flores claims these weapons will get in their way, creating an excuse to disarm Alonzo and set the trap for his murder. De Flores removes Alonzo’s sword as well as his own, although De Flores secretly carries a hidden weapon. Alonzo trusts De Flores and thanks him for his help, calling him “kind De Flores” (3.1.9). The two men venture further into the castle vault.

The rest of the castle believes Alonzo is on a boat trip away from the castle. Ironically, Alonzo is thankful for this secret. Alonzo believes this grants him time to view the castle at a relaxed pace, while in reality it aids the murder plot.

De Flores draws Alonzo’s attention to various points of interest. While Alonzo is distracted, De Flores appears behind him with a rapier and fatally stabs Alonzo. Once Alonzo is dead, De Flores notices Alonzo is wearing a diamond ring. De Flores tries to remove the ring, planning to show it to Beatrice as proof of the murder’s success. The ring proves difficult to remove, so De Flores cuts off Alonzo’s finger before removing Alonzo’s body from the passage.