 Maddalena is married to the artist Genaro, but is having an affair (in disguise) with Genaro's friend, the alchemist Stenio.Stenio tells Genaro of the mysterious woman who has seduced him, and then recognises Maddalena as his seductress.Initially both men turn on Maddalena but she encourages them to fight each other; Genaro kills Stenio, but is wounded himself in the process.