I Gioielli della Madonna (The Jewels of the Madonna) concerns a love triangle between the blacksmith Gennaro; his adopted sister Maliella; and Rafaele, the head of the local Camorra (the Neapolitan Mafia).

Act I
Naples, on the day of the Festival of the Madonna (July 16th). The city is alive with the festivities for the procession of the Madonna del Carmine when Rafaele tells Maliella that he loves her so much that he would even steal the jewels from the Madonna for her. Frightened, she runs away and the procession continues to its massive conclusion.

Act II
The garden in front of Gennaro’s and Maliella’s home, after dinner the same day. Gennaro declares his love for Maliella but she rebuffs him saying that she thinks of him only as a brother and loves Rafaele instead, telling him of Rafaele’s boast about the jewels. To prove his love, Gennaro decides to steal them himself. Returning later that evening, he gives them to Maliella who is overwhelmed by their beauty and puts them on, imagining herself in Rafaele’s arms. But it is Gennaro who embraces her and, in a daze, she falls into his arms.

Act III
The Camorra’s hideout, later that night. During a wild dance, Maliella runs in disheveled and confused. She begs Rafaele to save her from Gennaro and Rafaele orders his men to intercept him; but soon realizing that she has given herself to Gennaro, he throws her to the floor loosening her shawl and revealing the jewels. Gennaro is brought in and the Camorrists, horrified at the sacrilege, run away followed by Maliella who, cursing him, throws the jewels to the floor and runs to the sea to drown herself. Now alone, Gennaro prays to the Madonna for a sign of forgiveness. As dawn breaks, a ray of sunlight shines through the window onto the jewels. Taking this as the sign he had hoped for, Gennaro plunges a dagger into his heart as the birds sing to the dawn.