four o'clock
`` For even if there is n't any shooting from across No Man 's Land , '' explained Captain Black , `` a hostile aircraft may drop a bomb that will scatter a lot of steel bullets around . So wear your helmets and keep the cases on your cameras . '' It was a week after this , during which time there had been several false alarms of a big German attack , that one evening as they were about to turn in after having given a moving picture show an orderly came up to Blake . `` You and your two friends will report to Captain Black at four o'clock to-morrow morning , '' said the orderly . `` Why that hour ? '' asked Joe curiously . `` We 're going over the top , '' was the answer .