Dark secrets never stay submerged for long. Swept into the bright hustle-bustle of New York, Lily, Robert and Malkin discover that danger lies beneath the city's surface. For there are chilling goings-on... A strange boy held captive who needs their help, and a shadowy professor with a treacherous plan. Searching for clues, Robert and Lily are plunged into deep water... But will they uncover the deadly truth in time to survive?