about midnight
`` However , on payment of another mark each , you may perchance obtain the liberty of taking the air , on passing your word that you will make no attempt to leave the prison . '' The money and the promise were at once given , and the boys were told that at certain hours of the day they would have liberty to take the air in the courtyard below . The very thought of this gave the boys considerable satisfaction . They did not sleep soundly that night , and both were awoke , it might have been about midnight , by hearing groans , as of a person in pain , proceeding apparently from the chamber below them . They listened attentively , and now they heard a human voice ; it seemed lifted up in prayer . Getting out of bed , and putting their ears to the floor , they could distinguish the very words . Fervent and earnest was the prayer .