At twenty-five years old Anna, Lady Quartermain, becomes a grieving but wealthy widow. In an attempt to restart her life she sets up the Wellington Bureau, an investigation agency, without any serious expectation of it being a success. A series of cases follow in which Anna unravels a number of mysteries, including those surrounding the fabulous Quartermain Stone - a diamond brought into the family by Henry Quartermain at the beginning of the thirteenth century, and which has a long and eventful history. Anna also has to come to terms with the secrets and deceptions of the taciturn Brigadier Harris Butterworth, her dearest friend, whose involvement in covert operations brings danger into the lives of those she loves. The Wellington Bureau The Eleventh Commandment The Five Gold Rings Mystery The Fifth Plinth The Quartermain Stone Mystery