Leonardo da Vinci is painting a portrait and hating every minute of it when an animal of a type he's never seen before wanders into his studio. It turns out that it is a pet from another world accidentally left in his locale and era by a time traveler who wants it back. And once he learns who is belongs to Leonardo wants to know about the future. Eventually they make an uneasy trade and his visitor helps him create one of his most famous paintings while Leonardo tries to unlock the secrets that lay ahead and shows him the Milan of the Renaissance in this riveting novel by 5-time Hugo winner Mike Resnick.