six o'clock
`` More than that , the summons was handed me only twenty minutes ago . '' `` How was that ? '' the babu asked . `` It was sent at six o'clock . '' `` I was at work in the laboratory and had left orders I was not to be disturbed . But for one thing '' -- the petulance of Thirteen 's habitual expression was lightened by a flash of self-gratulation , and his voice shook a little with excitement -- `` I might not have received the summons before morning . '' `` And that one thing ? ''