"The Greatest English Detective Club #1" tells the story of stolen money and gold from an old exhibit hall which holds the history of diving and local shipwrecks, and ultimately how a young brother and sister solve it. For Phil Marsden, an eleven year old boy, his one and only mission is to solve mysteries like his mum who is both a history professor at Southampton University and a psychic who helps the Weymouth, England police on certain cases. For Kate Marsden, a ten year old girl, she desperately wants to keep up with her brother, not only to help him solve mysteries, but also to follow in her mum's footsteps.