The man who had been able to introduce himself here so mysteriously and to leave so many evidences against Daddy Jacques, was, there can be no doubt, familiar with the house.
At what hour exactly he entered, whether in the afternoon or in the evening, I cannot say.

One familiar with the proceedings and persons of this pavilion could choose his own time for entering The Yellow Room." "He could not have entered it if anybody had been in the laboratory," said Monsieur de Marquet.
"How do we know that ?" replied Larsan.

"There was the dinner in the laboratory, the coming and going of the servants in attendance.

There was a chemical experiment being carried on between ten and eleven o'clock, with Monsieur Stangerson, his daughter, and Daddy Jacques engaged at the furnace in a corner of the high chimney.

Who can say that the murderer--an intimate!--a friend!--did not take advantage of that moment to slip into The Yellow Room, after having taken off his boots in the lavatory ?" "It is very improbable," said Monsieur Stangerson.
"Doubtless--but it is not impossible.