The Spring of the Ram by Dorothy Dunnett Paperback Book 9780140113594

In 1461 the mysterious enigmatic Nicholas is in Florence Backed by none other than Cosimo de Medici he will sail the Black Sea to Trebizond the last jewel missing from the crown of the Ottoman Empire But trouble lies ahead Nicholas stepdaughter has eloped with his rival in trade a Machiavellian Genoese who races ahead of Nicholas