Peabody and Sherman travel back to ancient Rome, where Emperor Nero is set to perform a grand concert. However, recent fires in the city have led to rumors that Nero is responsible for them, putting his reputation at risk. Determined to clear Nero's name, Peabody must investigate the true cause of the fires while preventing any further disasters from occurring. As they navigate the chaotic Roman landscape, Peabody employs his cleverness and ingenuity to uncover the truth, ultimately helping Nero reclaim his honor and save the concert.