Leonardo da Vinci, twelve years old and a bastard, leaves the Tuscan countryside to join his father in Florence with dreams of becoming a painter. Francesco Salviati, also a bastard and scorned for his too-dark skin, dedicates himself to the Catholic Church with grand hopes of salvation. Towering above them both is Lorenzo de' Medici, barely a man, yet soon to be the patriarch of the world's wealthiest and most influential bank. Each of these young men harbors profound ambition, anxious to prove their potential to their superiors―and to themselves. Each is, in his own way, a son of Florence. Each will, when their paths cross, shed blood on Florence's streets.

Fifteenth-century Florence flourishes as a haven of breathtaking artistic, cultural, and technological innovation, but discord churns below the surface: the Medici's bank exacerbates the city's staggering wealth inequality, and rumors swirl of a rift between Lorenzo and the new pope. Meanwhile, the city has become Europe's preeminent destination for gay men―or "florenzers," as they come to be crudely called. For Leonardo, an astonishingly gifted painter's apprentice, being a florenzer might feel like personal liberation―but risk lingers around every corner.