Why indeed? That is exactly what the professor finds great
difficulty in explaining to her. An "old man" of "fifty" might very
easily give a home to a young girl, without comment from the world.
But then if an "old man of fifty" _wasn't_ an old man of fifty----
The professor checks his thoughts, they are growing too mixed.

"We should have been _so_ happy," Perpetua is going on, her tone
regretful. "We could have gone everywhere together, you and I. I
should have taken you to the theatre, to balls, to concerts, to
afternoons. You would have been _so_ happy, and so should I. You
would--wouldn't you?"

The professor nods his head. The awful vista she has opened up to
him has completely deprived him of speech.

"Ah! yes," sighs she, taking that deceitful nod in perfect good
faith. "And you would have been good to me too, and let me look in
at the shop windows. I should have taken such _care_ of you, and
made your tea for you, just" sadly, "as I used to do for poor papa,
and----"

It is becoming too much for the professor.

"It is late. I must go," says he.

It is a week later when he meets her again. The season is now at its
height, and some stray wave of life casting the professor into a
fashionable thoroughfare, he there finds her.