It appears that someone must have told him.
One night when the moon lay white on the trees and housetops, Miss Betty paused in her evening promenade and seated herself upon a bench on the borders of the garden, "touched," as the books of the time would have put it, "by the sweet tranquillity of the scene," and wrought upon by the tender incentive to sighs and melancholy which youth in loneliness finds in a loveliness of the earth.

The breeze bore the smells of the old-fashioned garden, of violets and cherry blossoms, and a sound of distant violins came on the air playing the new song from the new opera.
"But I also dreamt, which pleased me most, That you loved me just the same--" they sang; and with the lilt of them and the keen beauty of the night, the inherited pain of the ages rose from the depths of the young girl's heart, so that she thought it must break; for what reason she could not have told, since she was without care or sorrow that she knew, except the French Revolution, yet tears shone upon the long lashes.

She shook them off and looked up with a sudden odd consciousness.

The next second she sprang to her feet with a gasp and a choked outcry, her bands pressed to her breast.
Ten paces in front of her, a gap in the shrubbery where tall trees rose left a small radiant area of illumination like that of a lime-light in a theatre, its brilliancy intensified by the dark foliage behind.

It was open to view only from the bench by which she stood, and appeared, indeed, like the stage of a little theatre a stage occupied by a bizarre figure.