They walked to the rear of the institution and Robert pointed up through the tree at the window.
As they looked up Mrs. Vernon's face appeared from behind the bars.
"There she is!" cried Robert. "I wish I could attract her attention."
He decided to climb the tree again, and aided by the detective he went up with all possible speed.
One branch grew closer to the window than the others, and Robert went out on this as far as he dared. Then he waved his handkerchief.
Even in the darkness the white object fluttering in the wind attracted Mrs. Vernon's attention, and she looked intently in the direction.
At last she recognized Robert, and her face showed her joy. She had had the window shut to exclude the cool night air, but now she raised the sash.
"Robert!" she cried softly. "Oh, how glad I am that you have come!"
"Don't speak too loudly, Mrs. Vernon, or they may hear you."
"Are you alone?"