The mermaid secret

"Kallie and Danya are as unalike as twin sisters can be. When a mermaid visits Kallie in the night, asking for help, she accepts right away. Danya is harder to convince. But soon the twins are taking the plunge together into the amazing undersea world of Ayralon. A secret from their past awaits them--and a thrilling quest for the stolen magic of the merpeople"--Page 4 of cover.