Phantom- Box Five Explanation

  If the reader will visit the Opera one morning and ask leave to stroll where he pleases, without being accompanied by a stupid guide, let him go to Box Five and knock with his fist or stick on the enormous column that separates this from the stage-box. He will find that the column sounds hollow. After that, do not be astonished by the suggestion that it was occupied by the voice of the ghost: there is room inside the column for two men. If you are surprised that, when the various incidents occurred, no one turned round to look at the column, you must remember that it presented the appearance of solid marble, and that the voice contained in it seemed rather to come from the opposite side, for, as we have seen, the ghost was an expert ventriloquist.

-Epilogue