four o'clock
A little later a farm wagon , drawn by a pair of horses , stopped near the group . `` Now , you must excuse us , boys , '' announced Laura , rising with a mysterious air . `` We girls have a little errand to perform . We shall be back before half-past four o'clock . '' `` Would n't it be better to be back a good deal before that time ? '' urged Dick . `` You see , we ca n't carry more than three passengers at once , and we are to have eleven guests to ferry across the lake . ''