Somebody is stealing diamonds from the jeweller Mohammed Carat and it looks like the culprit is someone on his staff. Is it the standoffish goldsmith Danny Braveheart, who was supposed to have owned the whole shop? Possibly Luke Smith, the recently hired fitness fanatic with a taste for the good things in life? It surely can't be Vivian Leander, the loyal shop assistant who is now short of money. The police in the little town of Valleby are stuck, so they contact young detectives Jerry and Maya. They are in the same class at school and run a little detective agency together and as they well know, in the world of detective stories, even tiny clue is worth its weight in gold.