Death Sets Sail by Robin Stevens

Daisy Wells and Hazel Wong are in Egypt, where they are taking a cruise along the Nile. They are hoping to see some ancient temples and a mummy or two; what they get, instead, is murder.

Also travelling on the SS Hatshepsut is a mysterious society called the Breath of Life: a group of who believe themselves to be reincarnations of the ancient pharaohs. Three days into the cruise their leader, Theodora Miller, is found dead in her cabin. It soon becomes clear to Daisy and Hazel that Theodora’s timid daughter Hephzibah, who is prone to sleepwalking, is being framed. And within the society, everyone has a reason to want Theodora dead…