Showing Death in the Floating City by Tasha Alexander

The past does not give its secrets up easily...

Years ago, Emily's childhood nemesis, Emma Callum, scandalised society when she eloped with an Italian count. Now her father-in-law lies murdered, and her husband has fled, making him the prime suspect. Alone in her empty palazzo, Emma realises there's no one she can turn to for help but Emily, who leaves at once for Venice, with her husband.

When a fifteenth-century ring is found in the hand of the slain man, the mysteries of past and present become entwined, and in order to find the murderer, Emily must first unravel the secret of a centuries-old love affair...