midnight
`` Let 's put our heads together for a moment and work it out . Supposing you go to Weevil and tell him straight out that you were n't in your dorm last night , but with me . He contradicts you point-blank . ` You could not have been with Moncrief , because I looked in at his dormitory at midnight and saw that no one else was there . ' Then you bring forward your next piece , and cry , ` I think I can prove to you , sir , that I was in Dormitory X last night . ' ` Your proof , quick ! ' ` My proof is that as I was passing by your room I happened to glance in at the window , and saw you with another gentleman -- ahem !