midnight
`` Then if we are fortunate enough to find Uncle Felix before that time has expired , what shall we do , sir ? '' asked the precise Bob , who was always keeping an eye out for the legal aspect of things . `` Coax him to accompany you to the nearest notary public , where he can sign his acceptance of the terms under which he holds the option on the San Bernardino . But if this happens after the thirtieth it is all wasted energy ; for at midnight of that day , I happen to know , the option expires , '' the ranchman continued , somewhat impressively . Just as he finished speaking he suddenly turned toward the window , at which his keen vision had caught sight of a moving shadow , as though someone might have been crouching without , and listening . `` Who is there at the window ? '' he called out , sternly .