four o'clock
`` Then you must go very early to-morrow morning , before the detective gets up . '' I could n't help smiling at the notion of getting up before a detective . `` I am only too willing , '' I said . `` It must be by four o'clock , '' Miss Thorn went on energetically , `` and we must have a guide we can trust . Arrange it with one of Uncle Fenelon 's friends . '' `` We ? '' I repeated .