The Winking Ruby Mystery — Carolyn Keene

"Save Carlo . . . winking ruby . . . hurry!" This plea uttered by Gino, a mysterious violinist, just before he lapses into a coma, launch Jean and Louise Dana on their first exciting adventure in Europe. Is the mysterious "ruby" a gem, a girl, or part of a secret code?" The Danas must find out -- and fast -- because a life is at stake.

Danger stalks the young detectives from the moment they board the Balaska with their Uncle Ned, captain of the ocean liner. Crossing the Atlantic they meet Enrico and Lena Dotti, professional hypnotists, who offer to help in solving the puzzle. Jean wants to accept, but Louise is suspicious of the Dottis.

In Europe, the sisters discover that Gino's family has disappeared, driven into hiding by blackmail and threats of mal occhio, the evil eye. Probing deeper into the strange riddle, Jean and Louise become enmeshed in a mystery more frightening than the dungeon in which they are imprisoned. How they extricate themselves and locate a fabulous crimson gem make a pulse-quickening story.