This tenth sequel to The Book in the Loft series sends Neil MacBruce and the crew of the Circle of Planets’ starship Explorer to investigate a suspected world below the waters of an ocean covering the entire surface of a strange planet. Who or what resides below the water? And if there is something there, how and why did it come to be there? Explorer was built to ply the waves of space, not the waves of the deep. The mystery they set out to solve has answers, but they come in strange ways—and the outcome in an even stranger way.