Paolo is frightened. He is furious with Simon and decides he must poison him. Fiesco and Gabriele are brought in. He tells Fiesco he can be free if he murders Simon. Fiesco refuses. Just as Fiesco and Gabriele are about to leave, Paolo asks Gabriele whether he knows Amelia is here in the palace having an affair with Simon. Gabriele is furious. When Amelia enters she denies the story. She tells Gabriele she loves him and tries to persuade him to leave, but Simon is coming and Gabriele hides.