Three deliveries -- The letter is dead -- Lost in the art -- Picasso's lie -- Worms, snakes, and periwinkles -- The geographer's box -- The man on the wall -- A halloween surprise -- The blue ones -- Inside the puzzle --Nightmare -- Tea at four -- X the experts -- Flashing lights -- Murder and hot chocolate -- A morning in the dark -- What happens now? -- A bad fall -- The shock on the stairs -- A maniac -- Looking and seeing -- Twelves -- Help! -- The pieces.

When strange and seemingly unrelated events start to happen and a precious Vermeer painting disappears, eleven-year-olds Petra and Calder combine their talents to solve an international art scandal.