about four
o’clock
The usher hurried to the side door , opened it , and disappeared . The door remained open , while all eyes turned expectantly towards it . The clerk re-appeared and , stepping forward , said : `` Monsieur President , Frederic Larsan is not here . He left at about four o'clock and has not been seen since . '' `` That is my proof ! '' cried Rouletabille , triumphantly . `` Explain yourself ? ''