Third in the intriguing Leonardo da Vinci mystery series known for "capturing the essence of 15th-century Milan ".

As court engineer to the Duke of Milan, Leonardo da Vinci turns his superior mind to many pursuits – from outlandish contraptions to the odd murder…

With war looming ever closer, the iron-fisted Duke of Milan calls upon Master da Vinci to invent the deadliest weapon ever – a flying machine. So da Vinci calls in a craftsman who happens to be father to his star apprentice, Dino.

But da Vinci does not know that Dino is actually the craftsman's daughter, Delfina, who keeps her gender a secret to serve as apprentice. But as Delfina worries that her father will prove her undoing, someone murders another apprentice. Now, as her master works his brilliance, Delfina can only pray that no other apprentice – including herself – will fall victim.