about nine o'clock
`` My dear Wrayson , '' he expostulated , `` is this the sort of thing a man invents for fun ? Do listen for a moment , if you can , in patience . It is a deeply interesting case . If you remember , it was about nine o'clock when we left Luigi 's ; Bentham must have gone almost straight to his office , for he was found there dead a very few minutes after ten . '' `` Who killed him , and why ? '' Wrayson asked breathlessly . `` That , I suppose , we shall know later , '' the Colonel answered .