While the Roman general Scipio is sleeping in the palace of Massinissa, the allegorical figures Fortuna (Fortune) and Constanza (Constancy) appear to him in a dream, demanding that he choose one of them as his life-long companion. Fortuna possesses all the world’s riches and Constanza its wisdom. Scipio wants to know more before deciding on one of them, but Fortuna, in particular, is reluctant to grant him further time, admitting that she is as changeable and capricious as the wind. As Scipio admires the astonishing beauty of his surroundings, Costanza explains to him that on earth we are incapable of recognising such wonders, just as we have to turn away when trying to look into the sun.
Scipio asks who dwells in Elysium, and is immediately visited by a cortege of dead heroes who include his father Emilio and his adoptive grandfather Publio. The latter tells Scipio that only their mortal bodies are dead and urges him to live a virtuous life so that he can in time join the immortal heroes. Scipio is perturbed that his father Emilio does not seem happy about meeting him, but Emilio answers that in heaven happiness is a much calmer and less demonstrative emotion. Scipio wants to stay in Elysium, but Constanza and Fortuna insist that it is not yet permitted, while Publio and Emilio remind him that he has to return to earth and fulfil the path of destiny for the good of Rome.
The time has come for Scipio to decide between Fortuna and Constanza. One after the other, Fortuna and Constanza attempt to persuade Scipione, Fortuna claiming that the fate of men is determined by her free will alone while Constanza asserts that only she can withstand Fortuna and reward virtue. Scipio thus chooses Constanza. While Fortuna is summoning a terrible storm in her fury, Scipio reawakens in the palace in Massinissa and recognizes his dream’s omen. He resolves to commit himself to constancy rather than fortune.
In the final scene, the muse Licenza sums up the dream’s moral and declares that the story was not so much about Scipio as about Mozart’s patron, the Archbishop Colloredo.