The daughter of two employees of a cruise ship joins forces with the son of the new captain to solve a not-very-exciting puzzle aboard the luxury liner. In this first in a series of mysteries at sea, 11-year-old Philippa and Philip, who turns out to be much more than he seems, capture the unwanted attention of a flamboyant “duchess” and her obnoxious, larcenous nephews. Dogs with jeweled collars, parrots both genuine and mechanical and a mad scramble for hidden diamonds form the backdrop for this uncompelling read that might appeal to younger, undemanding readers who like their mysteries to unravel slowly and simply. They’ll be glad that Philippa spells it all out for them, although she does it in an unconvincing voice—“I'm somewhat used to passengers treating me like a servant, but the way she was homing in on me was getting under my skin"—and with frequently unrealistic dialogue. Gerstein’s black-and-white illustrations are energetic and suggest the breadth and scope of a large vessel, but they're not enough to compensate for the story's flaws. Sail on by. (Mystery. 8-11)