two o'clock
The lights went out in the old house . The door of the dancing hall had been locked from the outside . Lieutenant Flemming Wolff remained alone in the room , having hidden himself in a dark corner where he had not been seen by the servants , who had extinguished the lights and locked the door . The night watchman had just called out two o'clock when the solitary guest found himself , still giddy from the heavy wine , alone in the great dark hall in front of the mysterious door . The windows were at only a slight elevation from the street , and a spring would take him to safety should his desire to remain there , or to solve the mystery of the sealed room , vanish . But next morning all the windows in the great hall were found closed , just as the servants had left them the night before . The night watchman reported that he had heard a hollow-sounding crash in that unoccupied part of the house during the night .